git/t/t3424-rebase-empty.sh

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rebase (interactive-backend): make --keep-empty the default Different rebase backends have different treatment for commits which start empty (i.e. have no changes relative to their parent), and the --keep-empty option was added at some point to allow adjusting behavior. The handling of commits which start empty is actually quite similar to commit b00bf1c9a8dd (git-rebase: make --allow-empty-message the default, 2018-06-27), which pointed out that the behavior for various backends is often more happenstance than design. The specific change made in that commit is actually quite relevant as well and much of the logic there directly applies here. It makes a lot of sense in 'git commit' to error out on the creation of empty commits, unless an override flag is provided. However, once someone determines that there is a rare case that merits using the manual override to create such a commit, it is somewhere between annoying and harmful to have to take extra steps to keep such intentional commits around. Granted, empty commits are quite rare, which is why handling of them doesn't get considered much and folks tend to defer to existing (accidental) behavior and assume there was a reason for it, leading them to just add flags (--keep-empty in this case) that allow them to override the bad defaults. Fix the interactive backend so that --keep-empty is the default, much like we did with --allow-empty-message. The am backend should also be fixed to have --keep-empty semantics for commits that start empty, but that is not included in this patch other than a testcase documenting the failure. Note that there was one test in t3421 which appears to have been written expecting --keep-empty to not be the default as correct behavior. This test was introduced in commit 00b8be5a4d38 ("add tests for rebasing of empty commits", 2013-06-06), which was part of a series focusing on rebase topology and which had an interesting original cover letter at https://lore.kernel.org/git/1347949878-12578-1-git-send-email-martinvonz@gmail.com/ which noted Your input especially appreciated on whether you agree with the intent of the test cases. and then went into a long example about how one of the many tests added had several questions about whether it was correct. As such, I believe most the tests in that series were about testing rebase topology with as many different flags as possible and were not trying to state in general how those flags should behave otherwise. Signed-off-by: Elijah Newren <newren@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2020-02-15 21:36:24 +00:00
#!/bin/sh
test_description='git rebase of commits that start or become empty'
. ./test-lib.sh
test_expect_success 'setup test repository' '
test_write_lines 1 2 3 4 5 6 7 8 9 10 >numbers &&
test_write_lines A B C D E F G H I J >letters &&
git add numbers letters &&
git commit -m A &&
git branch upstream &&
git branch localmods &&
git checkout upstream &&
test_write_lines A B C D E >letters &&
git add letters &&
git commit -m B &&
test_write_lines 1 2 3 4 five 6 7 8 9 ten >numbers &&
git add numbers &&
git commit -m C &&
git checkout localmods &&
test_write_lines 1 2 3 4 five 6 7 8 9 10 >numbers &&
git add numbers &&
git commit -m C2 &&
git commit --allow-empty -m D &&
test_write_lines A B C D E >letters &&
git add letters &&
git commit -m "Five letters ought to be enough for anybody"
'
rebase: rename the two primary rebase backends Two related changes, with separate rationale for each: Rename the 'interactive' backend to 'merge' because: * 'interactive' as a name caused confusion; this backend has been used for many kinds of non-interactive rebases, and will probably be used in the future for more non-interactive rebases than interactive ones given that we are making it the default. * 'interactive' is not the underlying strategy; merging is. * the directory where state is stored is not called .git/rebase-interactive but .git/rebase-merge. Rename the 'am' backend to 'apply' because: * Few users are familiar with git-am as a reference point. * Related to the above, the name 'am' makes sentences in the documentation harder for users to read and comprehend (they may read it as the verb from "I am"); avoiding this difficult places a large burden on anyone writing documentation about this backend to be very careful with quoting and sentence structure and often forces annoying redundancy to try to avoid such problems. * Users stumble over pronunciation ("am" as in "I am a person not a backend" or "am" as in "the first and thirteenth letters in the alphabet in order are "A-M"); this may drive confusion when one user tries to explain to another what they are doing. * While "am" is the tool driving this backend, the tool driving git-am is git-apply, and since we are driving towards lower-level tools for the naming of the merge backend we may as well do so here too. * The directory where state is stored has never been called .git/rebase-am, it was always called .git/rebase-apply. For all the reasons listed above: * Modify the documentation to refer to the backends with the new names * Provide a brief note in the documentation connecting the new names to the old names in case users run across the old names anywhere (e.g. in old release notes or older versions of the documentation) * Change the (new) --am command line flag to --apply * Rename some enums, variables, and functions to reinforce the new backend names for us as well. Signed-off-by: Elijah Newren <newren@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2020-02-15 21:36:41 +00:00
test_expect_failure 'rebase (apply-backend)' '
rebase (interactive-backend): make --keep-empty the default Different rebase backends have different treatment for commits which start empty (i.e. have no changes relative to their parent), and the --keep-empty option was added at some point to allow adjusting behavior. The handling of commits which start empty is actually quite similar to commit b00bf1c9a8dd (git-rebase: make --allow-empty-message the default, 2018-06-27), which pointed out that the behavior for various backends is often more happenstance than design. The specific change made in that commit is actually quite relevant as well and much of the logic there directly applies here. It makes a lot of sense in 'git commit' to error out on the creation of empty commits, unless an override flag is provided. However, once someone determines that there is a rare case that merits using the manual override to create such a commit, it is somewhere between annoying and harmful to have to take extra steps to keep such intentional commits around. Granted, empty commits are quite rare, which is why handling of them doesn't get considered much and folks tend to defer to existing (accidental) behavior and assume there was a reason for it, leading them to just add flags (--keep-empty in this case) that allow them to override the bad defaults. Fix the interactive backend so that --keep-empty is the default, much like we did with --allow-empty-message. The am backend should also be fixed to have --keep-empty semantics for commits that start empty, but that is not included in this patch other than a testcase documenting the failure. Note that there was one test in t3421 which appears to have been written expecting --keep-empty to not be the default as correct behavior. This test was introduced in commit 00b8be5a4d38 ("add tests for rebasing of empty commits", 2013-06-06), which was part of a series focusing on rebase topology and which had an interesting original cover letter at https://lore.kernel.org/git/1347949878-12578-1-git-send-email-martinvonz@gmail.com/ which noted Your input especially appreciated on whether you agree with the intent of the test cases. and then went into a long example about how one of the many tests added had several questions about whether it was correct. As such, I believe most the tests in that series were about testing rebase topology with as many different flags as possible and were not trying to state in general how those flags should behave otherwise. Signed-off-by: Elijah Newren <newren@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2020-02-15 21:36:24 +00:00
test_when_finished "git rebase --abort" &&
git checkout -B testing localmods &&
rebase: rename the two primary rebase backends Two related changes, with separate rationale for each: Rename the 'interactive' backend to 'merge' because: * 'interactive' as a name caused confusion; this backend has been used for many kinds of non-interactive rebases, and will probably be used in the future for more non-interactive rebases than interactive ones given that we are making it the default. * 'interactive' is not the underlying strategy; merging is. * the directory where state is stored is not called .git/rebase-interactive but .git/rebase-merge. Rename the 'am' backend to 'apply' because: * Few users are familiar with git-am as a reference point. * Related to the above, the name 'am' makes sentences in the documentation harder for users to read and comprehend (they may read it as the verb from "I am"); avoiding this difficult places a large burden on anyone writing documentation about this backend to be very careful with quoting and sentence structure and often forces annoying redundancy to try to avoid such problems. * Users stumble over pronunciation ("am" as in "I am a person not a backend" or "am" as in "the first and thirteenth letters in the alphabet in order are "A-M"); this may drive confusion when one user tries to explain to another what they are doing. * While "am" is the tool driving this backend, the tool driving git-am is git-apply, and since we are driving towards lower-level tools for the naming of the merge backend we may as well do so here too. * The directory where state is stored has never been called .git/rebase-am, it was always called .git/rebase-apply. For all the reasons listed above: * Modify the documentation to refer to the backends with the new names * Provide a brief note in the documentation connecting the new names to the old names in case users run across the old names anywhere (e.g. in old release notes or older versions of the documentation) * Change the (new) --am command line flag to --apply * Rename some enums, variables, and functions to reinforce the new backend names for us as well. Signed-off-by: Elijah Newren <newren@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2020-02-15 21:36:41 +00:00
# rebase (--apply) should not drop commits that start empty
git rebase --apply upstream &&
rebase (interactive-backend): make --keep-empty the default Different rebase backends have different treatment for commits which start empty (i.e. have no changes relative to their parent), and the --keep-empty option was added at some point to allow adjusting behavior. The handling of commits which start empty is actually quite similar to commit b00bf1c9a8dd (git-rebase: make --allow-empty-message the default, 2018-06-27), which pointed out that the behavior for various backends is often more happenstance than design. The specific change made in that commit is actually quite relevant as well and much of the logic there directly applies here. It makes a lot of sense in 'git commit' to error out on the creation of empty commits, unless an override flag is provided. However, once someone determines that there is a rare case that merits using the manual override to create such a commit, it is somewhere between annoying and harmful to have to take extra steps to keep such intentional commits around. Granted, empty commits are quite rare, which is why handling of them doesn't get considered much and folks tend to defer to existing (accidental) behavior and assume there was a reason for it, leading them to just add flags (--keep-empty in this case) that allow them to override the bad defaults. Fix the interactive backend so that --keep-empty is the default, much like we did with --allow-empty-message. The am backend should also be fixed to have --keep-empty semantics for commits that start empty, but that is not included in this patch other than a testcase documenting the failure. Note that there was one test in t3421 which appears to have been written expecting --keep-empty to not be the default as correct behavior. This test was introduced in commit 00b8be5a4d38 ("add tests for rebasing of empty commits", 2013-06-06), which was part of a series focusing on rebase topology and which had an interesting original cover letter at https://lore.kernel.org/git/1347949878-12578-1-git-send-email-martinvonz@gmail.com/ which noted Your input especially appreciated on whether you agree with the intent of the test cases. and then went into a long example about how one of the many tests added had several questions about whether it was correct. As such, I believe most the tests in that series were about testing rebase topology with as many different flags as possible and were not trying to state in general how those flags should behave otherwise. Signed-off-by: Elijah Newren <newren@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2020-02-15 21:36:24 +00:00
test_write_lines D C B A >expect &&
git log --format=%s >actual &&
test_cmp expect actual
'
rebase (interactive-backend): fix handling of commits that become empty As established in the previous commit and commit b00bf1c9a8dd (git-rebase: make --allow-empty-message the default, 2018-06-27), the behavior for rebase with different backends in various edge or corner cases is often more happenstance than design. This commit addresses another such corner case: commits which "become empty". A careful reader may note that there are two types of commits which would become empty due to a rebase: * [clean cherry-pick] Commits which are clean cherry-picks of upstream commits, as determined by `git log --cherry-mark ...`. Re-applying these commits would result in an empty set of changes and a duplicative commit message; i.e. these are commits that have "already been applied" upstream. * [become empty] Commits which are not empty to start, are not clean cherry-picks of upstream commits, but which still become empty after being rebased. This happens e.g. when a commit has changes which are a strict subset of the changes in an upstream commit, or when the changes of a commit can be found spread across or among several upstream commits. Clearly, in both cases the changes in the commit in question are found upstream already, but the commit message may not be in the latter case. When cherry-mark can determine a commit is already upstream, then because of how cherry-mark works this means the upstream commit message was about the *exact* same set of changes. Thus, the commit messages can be assumed to be fully interchangeable (and are in fact likely to be completely identical). As such, the clean cherry-pick case represents a case when there is no information to be gained by keeping the extra commit around. All rebase types have always dropped these commits, and no one to my knowledge has ever requested that we do otherwise. For many of the become empty cases (and likely even most), we will also be able to drop the commit without loss of information -- but this isn't quite always the case. Since these commits represent cases that were not clean cherry-picks, there is no upstream commit message explaining the same set of changes. Projects with good commit message hygiene will likely have the explanation from our commit message contained within or spread among the relevant upstream commits, but not all projects run that way. As such, the commit message of the commit being rebased may have reasoning that suggests additional changes that should be made to adapt to the new base, or it may have information that someone wants to add as a note to another commit, or perhaps someone even wants to create an empty commit with the commit message as-is. Junio commented on the "become-empty" types of commits as follows[1]: WRT a change that ends up being empty (as opposed to a change that is empty from the beginning), I'd think that the current behaviour is desireable one. "am" based rebase is solely to transplant an existing history and want to stop much less than "interactive" one whose purpose is to polish a series before making it publishable, and asking for confirmation ("this has become empty--do you want to drop it?") is more appropriate from the workflow point of view. [1] https://lore.kernel.org/git/xmqqfu1fswdh.fsf@gitster-ct.c.googlers.com/ I would simply add that his arguments for "am"-based rebases actually apply to all non-explicitly-interactive rebases. Also, since we are stating that different cases should have different defaults, it may be worth providing a flag to allow users to select which behavior they want for these commits. Introduce a new command line flag for selecting the desired behavior: --empty={drop,keep,ask} with the definitions: drop: drop commits which become empty keep: keep commits which become empty ask: provide the user a chance to interact and pick what to do with commits which become empty on a case-by-case basis In line with Junio's suggestion, if the --empty flag is not specified, pick defaults as follows: explicitly interactive: ask otherwise: drop Signed-off-by: Elijah Newren <newren@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2020-02-15 21:36:25 +00:00
test_expect_success 'rebase --merge --empty=drop' '
git checkout -B testing localmods &&
git rebase --merge --empty=drop upstream &&
test_write_lines D C B A >expect &&
git log --format=%s >actual &&
test_cmp expect actual
'
test_expect_success 'rebase --merge uses default of --empty=drop' '
rebase (interactive-backend): make --keep-empty the default Different rebase backends have different treatment for commits which start empty (i.e. have no changes relative to their parent), and the --keep-empty option was added at some point to allow adjusting behavior. The handling of commits which start empty is actually quite similar to commit b00bf1c9a8dd (git-rebase: make --allow-empty-message the default, 2018-06-27), which pointed out that the behavior for various backends is often more happenstance than design. The specific change made in that commit is actually quite relevant as well and much of the logic there directly applies here. It makes a lot of sense in 'git commit' to error out on the creation of empty commits, unless an override flag is provided. However, once someone determines that there is a rare case that merits using the manual override to create such a commit, it is somewhere between annoying and harmful to have to take extra steps to keep such intentional commits around. Granted, empty commits are quite rare, which is why handling of them doesn't get considered much and folks tend to defer to existing (accidental) behavior and assume there was a reason for it, leading them to just add flags (--keep-empty in this case) that allow them to override the bad defaults. Fix the interactive backend so that --keep-empty is the default, much like we did with --allow-empty-message. The am backend should also be fixed to have --keep-empty semantics for commits that start empty, but that is not included in this patch other than a testcase documenting the failure. Note that there was one test in t3421 which appears to have been written expecting --keep-empty to not be the default as correct behavior. This test was introduced in commit 00b8be5a4d38 ("add tests for rebasing of empty commits", 2013-06-06), which was part of a series focusing on rebase topology and which had an interesting original cover letter at https://lore.kernel.org/git/1347949878-12578-1-git-send-email-martinvonz@gmail.com/ which noted Your input especially appreciated on whether you agree with the intent of the test cases. and then went into a long example about how one of the many tests added had several questions about whether it was correct. As such, I believe most the tests in that series were about testing rebase topology with as many different flags as possible and were not trying to state in general how those flags should behave otherwise. Signed-off-by: Elijah Newren <newren@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2020-02-15 21:36:24 +00:00
git checkout -B testing localmods &&
git rebase --merge upstream &&
test_write_lines D C B A >expect &&
git log --format=%s >actual &&
test_cmp expect actual
'
rebase (interactive-backend): fix handling of commits that become empty As established in the previous commit and commit b00bf1c9a8dd (git-rebase: make --allow-empty-message the default, 2018-06-27), the behavior for rebase with different backends in various edge or corner cases is often more happenstance than design. This commit addresses another such corner case: commits which "become empty". A careful reader may note that there are two types of commits which would become empty due to a rebase: * [clean cherry-pick] Commits which are clean cherry-picks of upstream commits, as determined by `git log --cherry-mark ...`. Re-applying these commits would result in an empty set of changes and a duplicative commit message; i.e. these are commits that have "already been applied" upstream. * [become empty] Commits which are not empty to start, are not clean cherry-picks of upstream commits, but which still become empty after being rebased. This happens e.g. when a commit has changes which are a strict subset of the changes in an upstream commit, or when the changes of a commit can be found spread across or among several upstream commits. Clearly, in both cases the changes in the commit in question are found upstream already, but the commit message may not be in the latter case. When cherry-mark can determine a commit is already upstream, then because of how cherry-mark works this means the upstream commit message was about the *exact* same set of changes. Thus, the commit messages can be assumed to be fully interchangeable (and are in fact likely to be completely identical). As such, the clean cherry-pick case represents a case when there is no information to be gained by keeping the extra commit around. All rebase types have always dropped these commits, and no one to my knowledge has ever requested that we do otherwise. For many of the become empty cases (and likely even most), we will also be able to drop the commit without loss of information -- but this isn't quite always the case. Since these commits represent cases that were not clean cherry-picks, there is no upstream commit message explaining the same set of changes. Projects with good commit message hygiene will likely have the explanation from our commit message contained within or spread among the relevant upstream commits, but not all projects run that way. As such, the commit message of the commit being rebased may have reasoning that suggests additional changes that should be made to adapt to the new base, or it may have information that someone wants to add as a note to another commit, or perhaps someone even wants to create an empty commit with the commit message as-is. Junio commented on the "become-empty" types of commits as follows[1]: WRT a change that ends up being empty (as opposed to a change that is empty from the beginning), I'd think that the current behaviour is desireable one. "am" based rebase is solely to transplant an existing history and want to stop much less than "interactive" one whose purpose is to polish a series before making it publishable, and asking for confirmation ("this has become empty--do you want to drop it?") is more appropriate from the workflow point of view. [1] https://lore.kernel.org/git/xmqqfu1fswdh.fsf@gitster-ct.c.googlers.com/ I would simply add that his arguments for "am"-based rebases actually apply to all non-explicitly-interactive rebases. Also, since we are stating that different cases should have different defaults, it may be worth providing a flag to allow users to select which behavior they want for these commits. Introduce a new command line flag for selecting the desired behavior: --empty={drop,keep,ask} with the definitions: drop: drop commits which become empty keep: keep commits which become empty ask: provide the user a chance to interact and pick what to do with commits which become empty on a case-by-case basis In line with Junio's suggestion, if the --empty flag is not specified, pick defaults as follows: explicitly interactive: ask otherwise: drop Signed-off-by: Elijah Newren <newren@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2020-02-15 21:36:25 +00:00
test_expect_success 'rebase --merge --empty=keep' '
git checkout -B testing localmods &&
git rebase --merge --empty=keep upstream &&
test_write_lines D C2 C B A >expect &&
git log --format=%s >actual &&
test_cmp expect actual
'
test_expect_success 'rebase --merge --empty=stop' '
git checkout -B testing localmods &&
test_must_fail git rebase --merge --empty=stop upstream &&
git rebase --skip &&
test_write_lines D C B A >expect &&
git log --format=%s >actual &&
test_cmp expect actual
'
rebase (interactive-backend): fix handling of commits that become empty As established in the previous commit and commit b00bf1c9a8dd (git-rebase: make --allow-empty-message the default, 2018-06-27), the behavior for rebase with different backends in various edge or corner cases is often more happenstance than design. This commit addresses another such corner case: commits which "become empty". A careful reader may note that there are two types of commits which would become empty due to a rebase: * [clean cherry-pick] Commits which are clean cherry-picks of upstream commits, as determined by `git log --cherry-mark ...`. Re-applying these commits would result in an empty set of changes and a duplicative commit message; i.e. these are commits that have "already been applied" upstream. * [become empty] Commits which are not empty to start, are not clean cherry-picks of upstream commits, but which still become empty after being rebased. This happens e.g. when a commit has changes which are a strict subset of the changes in an upstream commit, or when the changes of a commit can be found spread across or among several upstream commits. Clearly, in both cases the changes in the commit in question are found upstream already, but the commit message may not be in the latter case. When cherry-mark can determine a commit is already upstream, then because of how cherry-mark works this means the upstream commit message was about the *exact* same set of changes. Thus, the commit messages can be assumed to be fully interchangeable (and are in fact likely to be completely identical). As such, the clean cherry-pick case represents a case when there is no information to be gained by keeping the extra commit around. All rebase types have always dropped these commits, and no one to my knowledge has ever requested that we do otherwise. For many of the become empty cases (and likely even most), we will also be able to drop the commit without loss of information -- but this isn't quite always the case. Since these commits represent cases that were not clean cherry-picks, there is no upstream commit message explaining the same set of changes. Projects with good commit message hygiene will likely have the explanation from our commit message contained within or spread among the relevant upstream commits, but not all projects run that way. As such, the commit message of the commit being rebased may have reasoning that suggests additional changes that should be made to adapt to the new base, or it may have information that someone wants to add as a note to another commit, or perhaps someone even wants to create an empty commit with the commit message as-is. Junio commented on the "become-empty" types of commits as follows[1]: WRT a change that ends up being empty (as opposed to a change that is empty from the beginning), I'd think that the current behaviour is desireable one. "am" based rebase is solely to transplant an existing history and want to stop much less than "interactive" one whose purpose is to polish a series before making it publishable, and asking for confirmation ("this has become empty--do you want to drop it?") is more appropriate from the workflow point of view. [1] https://lore.kernel.org/git/xmqqfu1fswdh.fsf@gitster-ct.c.googlers.com/ I would simply add that his arguments for "am"-based rebases actually apply to all non-explicitly-interactive rebases. Also, since we are stating that different cases should have different defaults, it may be worth providing a flag to allow users to select which behavior they want for these commits. Introduce a new command line flag for selecting the desired behavior: --empty={drop,keep,ask} with the definitions: drop: drop commits which become empty keep: keep commits which become empty ask: provide the user a chance to interact and pick what to do with commits which become empty on a case-by-case basis In line with Junio's suggestion, if the --empty flag is not specified, pick defaults as follows: explicitly interactive: ask otherwise: drop Signed-off-by: Elijah Newren <newren@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2020-02-15 21:36:25 +00:00
test_expect_success 'rebase --merge --empty=ask' '
git checkout -B testing localmods &&
test_must_fail git rebase --merge --empty=ask upstream &&
git rebase --skip &&
test_write_lines D C B A >expect &&
git log --format=%s >actual &&
test_cmp expect actual
'
test_expect_success 'rebase --interactive --empty=drop' '
git checkout -B testing localmods &&
git rebase --interactive --empty=drop upstream &&
test_write_lines D C B A >expect &&
git log --format=%s >actual &&
test_cmp expect actual
'
test_expect_success 'rebase --interactive --empty=keep' '
git checkout -B testing localmods &&
git rebase --interactive --empty=keep upstream &&
test_write_lines D C2 C B A >expect &&
git log --format=%s >actual &&
test_cmp expect actual
'
test_expect_success 'rebase --interactive --empty=stop' '
rebase (interactive-backend): fix handling of commits that become empty As established in the previous commit and commit b00bf1c9a8dd (git-rebase: make --allow-empty-message the default, 2018-06-27), the behavior for rebase with different backends in various edge or corner cases is often more happenstance than design. This commit addresses another such corner case: commits which "become empty". A careful reader may note that there are two types of commits which would become empty due to a rebase: * [clean cherry-pick] Commits which are clean cherry-picks of upstream commits, as determined by `git log --cherry-mark ...`. Re-applying these commits would result in an empty set of changes and a duplicative commit message; i.e. these are commits that have "already been applied" upstream. * [become empty] Commits which are not empty to start, are not clean cherry-picks of upstream commits, but which still become empty after being rebased. This happens e.g. when a commit has changes which are a strict subset of the changes in an upstream commit, or when the changes of a commit can be found spread across or among several upstream commits. Clearly, in both cases the changes in the commit in question are found upstream already, but the commit message may not be in the latter case. When cherry-mark can determine a commit is already upstream, then because of how cherry-mark works this means the upstream commit message was about the *exact* same set of changes. Thus, the commit messages can be assumed to be fully interchangeable (and are in fact likely to be completely identical). As such, the clean cherry-pick case represents a case when there is no information to be gained by keeping the extra commit around. All rebase types have always dropped these commits, and no one to my knowledge has ever requested that we do otherwise. For many of the become empty cases (and likely even most), we will also be able to drop the commit without loss of information -- but this isn't quite always the case. Since these commits represent cases that were not clean cherry-picks, there is no upstream commit message explaining the same set of changes. Projects with good commit message hygiene will likely have the explanation from our commit message contained within or spread among the relevant upstream commits, but not all projects run that way. As such, the commit message of the commit being rebased may have reasoning that suggests additional changes that should be made to adapt to the new base, or it may have information that someone wants to add as a note to another commit, or perhaps someone even wants to create an empty commit with the commit message as-is. Junio commented on the "become-empty" types of commits as follows[1]: WRT a change that ends up being empty (as opposed to a change that is empty from the beginning), I'd think that the current behaviour is desireable one. "am" based rebase is solely to transplant an existing history and want to stop much less than "interactive" one whose purpose is to polish a series before making it publishable, and asking for confirmation ("this has become empty--do you want to drop it?") is more appropriate from the workflow point of view. [1] https://lore.kernel.org/git/xmqqfu1fswdh.fsf@gitster-ct.c.googlers.com/ I would simply add that his arguments for "am"-based rebases actually apply to all non-explicitly-interactive rebases. Also, since we are stating that different cases should have different defaults, it may be worth providing a flag to allow users to select which behavior they want for these commits. Introduce a new command line flag for selecting the desired behavior: --empty={drop,keep,ask} with the definitions: drop: drop commits which become empty keep: keep commits which become empty ask: provide the user a chance to interact and pick what to do with commits which become empty on a case-by-case basis In line with Junio's suggestion, if the --empty flag is not specified, pick defaults as follows: explicitly interactive: ask otherwise: drop Signed-off-by: Elijah Newren <newren@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2020-02-15 21:36:25 +00:00
git checkout -B testing localmods &&
test_must_fail git rebase --interactive --empty=stop upstream &&
rebase (interactive-backend): fix handling of commits that become empty As established in the previous commit and commit b00bf1c9a8dd (git-rebase: make --allow-empty-message the default, 2018-06-27), the behavior for rebase with different backends in various edge or corner cases is often more happenstance than design. This commit addresses another such corner case: commits which "become empty". A careful reader may note that there are two types of commits which would become empty due to a rebase: * [clean cherry-pick] Commits which are clean cherry-picks of upstream commits, as determined by `git log --cherry-mark ...`. Re-applying these commits would result in an empty set of changes and a duplicative commit message; i.e. these are commits that have "already been applied" upstream. * [become empty] Commits which are not empty to start, are not clean cherry-picks of upstream commits, but which still become empty after being rebased. This happens e.g. when a commit has changes which are a strict subset of the changes in an upstream commit, or when the changes of a commit can be found spread across or among several upstream commits. Clearly, in both cases the changes in the commit in question are found upstream already, but the commit message may not be in the latter case. When cherry-mark can determine a commit is already upstream, then because of how cherry-mark works this means the upstream commit message was about the *exact* same set of changes. Thus, the commit messages can be assumed to be fully interchangeable (and are in fact likely to be completely identical). As such, the clean cherry-pick case represents a case when there is no information to be gained by keeping the extra commit around. All rebase types have always dropped these commits, and no one to my knowledge has ever requested that we do otherwise. For many of the become empty cases (and likely even most), we will also be able to drop the commit without loss of information -- but this isn't quite always the case. Since these commits represent cases that were not clean cherry-picks, there is no upstream commit message explaining the same set of changes. Projects with good commit message hygiene will likely have the explanation from our commit message contained within or spread among the relevant upstream commits, but not all projects run that way. As such, the commit message of the commit being rebased may have reasoning that suggests additional changes that should be made to adapt to the new base, or it may have information that someone wants to add as a note to another commit, or perhaps someone even wants to create an empty commit with the commit message as-is. Junio commented on the "become-empty" types of commits as follows[1]: WRT a change that ends up being empty (as opposed to a change that is empty from the beginning), I'd think that the current behaviour is desireable one. "am" based rebase is solely to transplant an existing history and want to stop much less than "interactive" one whose purpose is to polish a series before making it publishable, and asking for confirmation ("this has become empty--do you want to drop it?") is more appropriate from the workflow point of view. [1] https://lore.kernel.org/git/xmqqfu1fswdh.fsf@gitster-ct.c.googlers.com/ I would simply add that his arguments for "am"-based rebases actually apply to all non-explicitly-interactive rebases. Also, since we are stating that different cases should have different defaults, it may be worth providing a flag to allow users to select which behavior they want for these commits. Introduce a new command line flag for selecting the desired behavior: --empty={drop,keep,ask} with the definitions: drop: drop commits which become empty keep: keep commits which become empty ask: provide the user a chance to interact and pick what to do with commits which become empty on a case-by-case basis In line with Junio's suggestion, if the --empty flag is not specified, pick defaults as follows: explicitly interactive: ask otherwise: drop Signed-off-by: Elijah Newren <newren@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2020-02-15 21:36:25 +00:00
git rebase --skip &&
test_write_lines D C B A >expect &&
git log --format=%s >actual &&
test_cmp expect actual
'
test_expect_success 'rebase --interactive uses default of --empty=stop' '
rebase (interactive-backend): make --keep-empty the default Different rebase backends have different treatment for commits which start empty (i.e. have no changes relative to their parent), and the --keep-empty option was added at some point to allow adjusting behavior. The handling of commits which start empty is actually quite similar to commit b00bf1c9a8dd (git-rebase: make --allow-empty-message the default, 2018-06-27), which pointed out that the behavior for various backends is often more happenstance than design. The specific change made in that commit is actually quite relevant as well and much of the logic there directly applies here. It makes a lot of sense in 'git commit' to error out on the creation of empty commits, unless an override flag is provided. However, once someone determines that there is a rare case that merits using the manual override to create such a commit, it is somewhere between annoying and harmful to have to take extra steps to keep such intentional commits around. Granted, empty commits are quite rare, which is why handling of them doesn't get considered much and folks tend to defer to existing (accidental) behavior and assume there was a reason for it, leading them to just add flags (--keep-empty in this case) that allow them to override the bad defaults. Fix the interactive backend so that --keep-empty is the default, much like we did with --allow-empty-message. The am backend should also be fixed to have --keep-empty semantics for commits that start empty, but that is not included in this patch other than a testcase documenting the failure. Note that there was one test in t3421 which appears to have been written expecting --keep-empty to not be the default as correct behavior. This test was introduced in commit 00b8be5a4d38 ("add tests for rebasing of empty commits", 2013-06-06), which was part of a series focusing on rebase topology and which had an interesting original cover letter at https://lore.kernel.org/git/1347949878-12578-1-git-send-email-martinvonz@gmail.com/ which noted Your input especially appreciated on whether you agree with the intent of the test cases. and then went into a long example about how one of the many tests added had several questions about whether it was correct. As such, I believe most the tests in that series were about testing rebase topology with as many different flags as possible and were not trying to state in general how those flags should behave otherwise. Signed-off-by: Elijah Newren <newren@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2020-02-15 21:36:24 +00:00
git checkout -B testing localmods &&
test_must_fail git rebase --interactive upstream &&
git rebase --skip &&
test_write_lines D C B A >expect &&
git log --format=%s >actual &&
test_cmp expect actual
'
rebase: reinstate --no-keep-empty Commit d48e5e21da ("rebase (interactive-backend): make --keep-empty the default", 2020-02-15) turned --keep-empty (for keeping commits which start empty) into the default. The logic underpinning that commit was: 1) 'git commit' errors out on the creation of empty commits without an override flag 2) Once someone determines that the override is worthwhile, it's annoying and/or harmful to required them to take extra steps in order to keep such commits around (and to repeat such steps with every rebase). While the logic on which the decision was made is sound, the result was a bit of an overcorrection. Instead of jumping to having --keep-empty being the default, it jumped to making --keep-empty the only available behavior. There was a simple workaround, though, which was thought to be good enough at the time. People could still drop commits which started empty the same way the could drop any commits: by firing up an interactive rebase and picking out the commits they didn't want from the list. However, there are cases where external tools might create enough empty commits that picking all of them out is painful. As such, having a flag to automatically remove start-empty commits may be beneficial. Provide users a way to drop commits which start empty using a flag that existed for years: --no-keep-empty. Interpret --keep-empty as countermanding any previous --no-keep-empty, but otherwise leaving --keep-empty as the default. This might lead to some slight weirdness since commands like git rebase --empty=drop --keep-empty git rebase --empty=keep --no-keep-empty look really weird despite making perfect sense (the first will drop commits which become empty, but keep commits that started empty; the second will keep commits which become empty, but drop commits which started empty). However, --no-keep-empty was named years ago and we are predominantly keeping it for backward compatibility; also we suspect it will only be used rarely since folks already have a simple way to drop commits they don't want with an interactive rebase. Reported-by: Bryan Turner <bturner@atlassian.com> Reported-by: Sami Boukortt <sami@boukortt.com> Signed-off-by: Elijah Newren <newren@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2020-04-11 02:44:25 +00:00
test_expect_success 'rebase --merge --empty=drop --keep-empty' '
git checkout -B testing localmods &&
git rebase --merge --empty=drop --keep-empty upstream &&
test_write_lines D C B A >expect &&
git log --format=%s >actual &&
test_cmp expect actual
'
test_expect_success 'rebase --merge --empty=drop --no-keep-empty' '
git checkout -B testing localmods &&
git rebase --merge --empty=drop --no-keep-empty upstream &&
test_write_lines C B A >expect &&
git log --format=%s >actual &&
test_cmp expect actual
'
test_expect_success 'rebase --merge --empty=keep --keep-empty' '
git checkout -B testing localmods &&
git rebase --merge --empty=keep --keep-empty upstream &&
test_write_lines D C2 C B A >expect &&
git log --format=%s >actual &&
test_cmp expect actual
'
test_expect_success 'rebase --merge --empty=keep --no-keep-empty' '
git checkout -B testing localmods &&
git rebase --merge --empty=keep --no-keep-empty upstream &&
test_write_lines C2 C B A >expect &&
git log --format=%s >actual &&
test_cmp expect actual
'
test_expect_success 'rebase --merge does not leave state laying around' '
git checkout -B testing localmods~2 &&
git rebase --merge upstream &&
test_path_is_missing .git/CHERRY_PICK_HEAD &&
test_path_is_missing .git/MERGE_MSG
'
test_expect_success 'rebase --exec --empty=drop' '
git checkout -B testing localmods &&
git rebase --exec "true" --empty=drop upstream &&
test_write_lines D C B A >expect &&
git log --format=%s >actual &&
test_cmp expect actual
'
test_expect_success 'rebase --exec --empty=keep' '
git checkout -B testing localmods &&
git rebase --exec "true" --empty=keep upstream &&
test_write_lines D C2 C B A >expect &&
git log --format=%s >actual &&
test_cmp expect actual
'
test_expect_success 'rebase --exec uses default of --empty=keep' '
git checkout -B testing localmods &&
git rebase --exec "true" upstream &&
test_write_lines D C2 C B A >expect &&
git log --format=%s >actual &&
test_cmp expect actual
'
test_expect_success 'rebase --exec --empty=stop' '
git checkout -B testing localmods &&
test_must_fail git rebase --exec "true" --empty=stop upstream &&
git rebase --skip &&
test_write_lines D C B A >expect &&
git log --format=%s >actual &&
test_cmp expect actual
'
rebase (interactive-backend): make --keep-empty the default Different rebase backends have different treatment for commits which start empty (i.e. have no changes relative to their parent), and the --keep-empty option was added at some point to allow adjusting behavior. The handling of commits which start empty is actually quite similar to commit b00bf1c9a8dd (git-rebase: make --allow-empty-message the default, 2018-06-27), which pointed out that the behavior for various backends is often more happenstance than design. The specific change made in that commit is actually quite relevant as well and much of the logic there directly applies here. It makes a lot of sense in 'git commit' to error out on the creation of empty commits, unless an override flag is provided. However, once someone determines that there is a rare case that merits using the manual override to create such a commit, it is somewhere between annoying and harmful to have to take extra steps to keep such intentional commits around. Granted, empty commits are quite rare, which is why handling of them doesn't get considered much and folks tend to defer to existing (accidental) behavior and assume there was a reason for it, leading them to just add flags (--keep-empty in this case) that allow them to override the bad defaults. Fix the interactive backend so that --keep-empty is the default, much like we did with --allow-empty-message. The am backend should also be fixed to have --keep-empty semantics for commits that start empty, but that is not included in this patch other than a testcase documenting the failure. Note that there was one test in t3421 which appears to have been written expecting --keep-empty to not be the default as correct behavior. This test was introduced in commit 00b8be5a4d38 ("add tests for rebasing of empty commits", 2013-06-06), which was part of a series focusing on rebase topology and which had an interesting original cover letter at https://lore.kernel.org/git/1347949878-12578-1-git-send-email-martinvonz@gmail.com/ which noted Your input especially appreciated on whether you agree with the intent of the test cases. and then went into a long example about how one of the many tests added had several questions about whether it was correct. As such, I believe most the tests in that series were about testing rebase topology with as many different flags as possible and were not trying to state in general how those flags should behave otherwise. Signed-off-by: Elijah Newren <newren@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2020-02-15 21:36:24 +00:00
test_done