Commit graph

263 commits

Author SHA1 Message Date
Junio C Hamano
a6f38c109b Merge branch 'bw/object-id'
Conversion from uchar[20] to struct object_id continues.

* bw/object-id: (33 commits)
  diff: rename diff_fill_sha1_info to diff_fill_oid_info
  diffcore-rename: use is_empty_blob_oid
  tree-diff: convert path_appendnew to object_id
  tree-diff: convert diff_tree_paths to struct object_id
  tree-diff: convert try_to_follow_renames to struct object_id
  builtin/diff-tree: cleanup references to sha1
  diff-tree: convert diff_tree_sha1 to struct object_id
  notes-merge: convert write_note_to_worktree to struct object_id
  notes-merge: convert verify_notes_filepair to struct object_id
  notes-merge: convert find_notes_merge_pair_ps to struct object_id
  notes-merge: convert merge_from_diffs to struct object_id
  notes-merge: convert notes_merge* to struct object_id
  tree-diff: convert diff_root_tree_sha1 to struct object_id
  combine-diff: convert find_paths_* to struct object_id
  combine-diff: convert diff_tree_combined to struct object_id
  diff: convert diff_flush_patch_id to struct object_id
  patch-ids: convert to struct object_id
  diff: finish conversion for prepare_temp_file to struct object_id
  diff: convert reuse_worktree_file to struct object_id
  diff: convert fill_filespec to struct object_id
  ...
2017-06-19 12:38:44 -07:00
Brandon Williams
fda94b416e tree-diff: convert diff_tree_paths to struct object_id
Signed-off-by: Brandon Williams <bmwill@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2017-06-05 11:23:58 +09:00
Brandon Williams
66f414f885 diff-tree: convert diff_tree_sha1 to struct object_id
Signed-off-by: Brandon Williams <bmwill@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2017-06-05 11:23:58 +09:00
Junio C Hamano
583c6a2295 Merge branch 'js/blame-lib'
The internal logic used in "git blame" has been libified to make it
easier to use by cgit.

* js/blame-lib: (29 commits)
  blame: move entry prepend to libgit
  blame: move scoreboard setup to libgit
  blame: move scoreboard-related methods to libgit
  blame: move fake-commit-related methods to libgit
  blame: move origin-related methods to libgit
  blame: move core structures to header
  blame: create entry prepend function
  blame: create scoreboard setup function
  blame: create scoreboard init function
  blame: rework methods that determine 'final' commit
  blame: wrap blame_sort and compare_blame_final
  blame: move progress updates to a scoreboard callback
  blame: make sanity_check use a callback in scoreboard
  blame: move no_whole_file_rename flag to scoreboard
  blame: move xdl_opts flags to scoreboard
  blame: move show_root flag to scoreboard
  blame: move reverse flag to scoreboard
  blame: move contents_from to scoreboard
  blame: move copy/move thresholds to scoreboard
  blame: move stat counters to scoreboard
  ...
2017-06-05 09:18:12 +09:00
Brandon Williams
7b8dea0c75 tree-diff: convert diff_root_tree_sha1 to struct object_id
Signed-off-by: Brandon Williams <bmwill@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2017-06-02 09:36:30 +09:00
Brandon Williams
b9acf54dbd combine-diff: convert diff_tree_combined to struct object_id
Signed-off-by: Brandon Williams <bmwill@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2017-06-02 09:36:07 +09:00
Brandon Williams
bd25f28876 diff: convert diff_flush_patch_id to struct object_id
Signed-off-by: Brandon Williams <bmwill@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2017-06-02 09:36:07 +09:00
Brandon Williams
94a0097a41 diff: convert diff_change to struct object_id
Convert diff_change to take a struct object_id.  In addition convert the
function pointer type 'change_fn_t' to also take a struct object_id.

Signed-off-by: Brandon Williams <bmwill@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2017-06-02 09:36:07 +09:00
Brandon Williams
c26022ea8f diff: convert diff_addremove to struct object_id
Convert diff_addremove to take a struct object_id.  In addtion convert
the function pointer type 'add_remove_fn_t' to also take a struct
object_id.

Signed-off-by: Brandon Williams <bmwill@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2017-06-02 09:36:07 +09:00
Jeff Smith
3a35cb2ea8 blame: move textconv_object with related functions
textconv_object is used in places other than blame.c and should be moved
to a more appropriate location.  Other textconv related functions are
located in diff.c so that seems as good a place as any.

Signed-off-by: Jeff Smith <whydoubt@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2017-05-24 15:41:50 +09:00
brian m. carlson
944cffbd18 diff-lib: convert do_diff_cache to struct object_id
This is needed to convert parse_tree_indirect.

Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2017-05-08 15:12:58 +09:00
brian m. carlson
910650d2f8 Rename sha1_array to oid_array
Since this structure handles an array of object IDs, rename it to struct
oid_array.  Also rename the accessor functions and the initialization
constant.

This commit was produced mechanically by providing non-Documentation
files to the following Perl one-liners:

    perl -pi -E 's/struct sha1_array/struct oid_array/g'
    perl -pi -E 's/\bsha1_array_/oid_array_/g'
    perl -pi -E 's/SHA1_ARRAY_INIT/OID_ARRAY_INIT/g'

Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2017-03-31 08:33:56 -07:00
Junio C Hamano
650360210a Merge branch 'nd/ita-empty-commit'
When new paths were added by "git add -N" to the index, it was
enough to circumvent the check by "git commit" to refrain from
making an empty commit without "--allow-empty".  The same logic
prevented "git status" to show such a path as "new file" in the
"Changes not staged for commit" section.

* nd/ita-empty-commit:
  commit: don't be fooled by ita entries when creating initial commit
  commit: fix empty commit creation when there's no changes but ita entries
  diff: add --ita-[in]visible-in-index
  diff-lib: allow ita entries treated as "not yet exist in index"
2016-10-27 14:58:50 -07:00
Jeff King
d6cece51b8 diff_aligned_abbrev: use "struct oid"
Since we're modifying this function anyway, it's a good time
to update it to the more modern "struct oid". We can also
drop some of the magic numbers in favor of GIT_SHA1_HEXSZ,
along with some descriptive comments.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2016-10-26 13:30:51 -07:00
Jeff King
d5e3b01e5b diff_unique_abbrev: rename to diff_aligned_abbrev
The word "align" describes how the function actually differs
from find_unique_abbrev, and will make it less confusing
when we add more diff-specific abbrevation functions that do
not do this alignment.

Since this is a globally available function, let's also move
its descriptive comment to the header file, where we
typically document function interfaces.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2016-10-26 13:30:51 -07:00
Nguyễn Thái Ngọc Duy
018ec3c820 commit: fix empty commit creation when there's no changes but ita entries
If i-t-a entries are present and there is no change between the index
and HEAD i-t-a entries, index_differs_from() still returns "dirty, new
entries" (aka, the resulting commit is not empty), but cache-tree will
skip i-t-a entries and produce the exact same tree of current
commit.

index_differs_from() is supposed to catch this so we can abort
git-commit (unless --no-empty is specified). Update it to optionally
ignore i-t-a entries when doing a diff between the index and HEAD so
that it would return "no change" in this case and abort commit.

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2016-10-24 10:48:23 -07:00
Nguyễn Thái Ngọc Duy
425a28e0a4 diff-lib: allow ita entries treated as "not yet exist in index"
When comparing the index and the working tree to show which paths are
new, and comparing the tree recorded in the HEAD and the index to see if
committing the contents recorded in the index would result in an empty
commit, we would want the former comparison to say "these are new paths"
and the latter to say "there is no change" for paths that are marked as
intent-to-add.

We made a similar attempt at d95d728a ("diff-lib.c: adjust position of
i-t-a entries in diff", 2015-03-16), which redefined the semantics of
these two comparison modes globally, which was a disaster and had to be
reverted at 78cc1a54 ("Revert "diff-lib.c: adjust position of i-t-a
entries in diff"", 2015-06-23).

To make sure we do not repeat the same mistake, introduce a new internal
diffopt option so that this different semantics can be asked for only by
callers that ask it, while making sure other unaudited callers will get
the same comparison result.

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2016-10-24 10:47:28 -07:00
Junio C Hamano
b7af6ae5cf Merge branch 'mh/diff-indent-heuristic'
Output from "git diff" can be made easier to read by selecting
which lines are common and which lines are added/deleted
intelligently when the lines before and after the changed section
are the same.  A command line option is added to help with the
experiment to find a good heuristics.

* mh/diff-indent-heuristic:
  blame: honor the diff heuristic options and config
  parse-options: add parse_opt_unknown_cb()
  diff: improve positioning of add/delete blocks in diffs
  xdl_change_compact(): introduce the concept of a change group
  recs_match(): take two xrecord_t pointers as arguments
  is_blank_line(): take a single xrecord_t as argument
  xdl_change_compact(): only use heuristic if group can't be matched
  xdl_change_compact(): fix compaction heuristic to adjust ixo
2016-09-26 16:09:16 -07:00
Michael Haggerty
5b162879e9 blame: honor the diff heuristic options and config
Teach "git blame" and "git annotate" the --compaction-heuristic and
--indent-heuristic options that are now supported by "git diff".

Also teach them to honor the `diff.compactionHeuristic` and
`diff.indentHeuristic` configuration options.

It would be conceivable to introduce separate configuration options for
"blame" and "annotate"; for example `blame.compactionHeuristic` and
`blame.indentHeuristic`. But it would be confusing to users if blame
output is inconsistent with diff output, so it makes more sense for them
to respect the same configuration.

Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2016-09-19 10:25:11 -07:00
Junio C Hamano
305d7f1339 Merge branch 'jk/diff-submodule-diff-inline'
The "git diff --submodule={short,log}" mechanism has been enhanced
to allow "--submodule=diff" to show the patch between the submodule
commits bound to the superproject.

* jk/diff-submodule-diff-inline:
  diff: teach diff to display submodule difference with an inline diff
  submodule: refactor show_submodule_summary with helper function
  submodule: convert show_submodule_summary to use struct object_id *
  allow do_submodule_path to work even if submodule isn't checked out
  diff: prepare for additional submodule formats
  graph: add support for --line-prefix on all graph-aware output
  diff.c: remove output_prefix_length field
  cache: add empty_tree_oid object and helper function
2016-09-12 15:34:31 -07:00
Jacob Keller
fd47ae6a5b diff: teach diff to display submodule difference with an inline diff
Teach git-diff and friends a new format for displaying the difference
of a submodule. The new format is an inline diff of the contents of the
submodule between the commit range of the update. This allows the user
to see the actual code change caused by a submodule update.

Add tests for the new format and option.

Signed-off-by: Jacob Keller <jacob.keller@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2016-08-31 18:07:10 -07:00
Jacob Keller
61cfbc054d diff: prepare for additional submodule formats
A future patch will add a new format for displaying the difference of
a submodule. Make it easier by changing how we store the current
selected format. Replace the DIFF_OPT flag with an enumeration, as each
format will be mutually exclusive.

Signed-off-by: Jacob Keller <jacob.keller@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2016-08-31 18:07:09 -07:00
Jacob Keller
660e113ce1 graph: add support for --line-prefix on all graph-aware output
Add an extension to git-diff and git-log (and any other graph-aware
displayable output) such that "--line-prefix=<string>" will print the
additional line-prefix on every line of output.

To make this work, we have to fix a few bugs in the graph API that force
graph_show_commit_msg to be used only when you have a valid graph.
Additionally, we extend the default_diff_output_prefix handler to work
even when no graph is enabled.

This is somewhat of a hack on top of the graph API, but I think it
should be acceptable here.

This will be used by a future extension of submodule display which
displays the submodule diff as the actual diff between the pre and post
commit in the submodule project.

Add some tests for both git-log and git-diff to ensure that the prefix
is honored correctly.

Signed-off-by: Jacob Keller <jacob.keller@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2016-08-31 18:07:09 -07:00
Junio C Hamano
cd48dadb8d diff.c: remove output_prefix_length field
"diff/log --stat" has a logic that determines the display columns
available for the diffstat part of the output and apportions it for
pathnames and diffstat graph automatically.

5e71a84a (Add output_prefix_length to diff_options, 2012-04-16)
added the output_prefix_length field to diff_options structure to
allow this logic to subtract the display columns used for the
history graph part from the total "terminal width"; this matters
when the "git log --graph -p" option is in use.

The field must be set to the number of display columns needed to
show the output from the output_prefix() callback, which is error
prone.  As there is only one user of the field, and the user has the
actual value of the prefix string, let's get rid of the field and
have the user count the display width itself.

Signed-off-by: Junio C Hamano <gitster@pobox.com>
2016-08-31 18:07:08 -07:00
Kevin Willford
3e8e32c32e patch-ids: add flag to create the diff patch id using header only data
This will allow a diff patch id to be created using only the header data
so that the contents of the file will not have to be loaded.

Signed-off-by: Kevin Willford <kcwillford@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2016-07-29 14:10:01 -07:00
Junio C Hamano
5d2a30d7d8 Merge branch 'mm/diff-renames-default'
The end-user facing Porcelain level commands like "diff" and "log"
now enables the rename detection by default.

* mm/diff-renames-default:
  diff: activate diff.renames by default
  log: introduce init_log_defaults()
  t: add tests for diff.renames (true/false/unset)
  t4001-diff-rename: wrap file creations in a test
  Documentation/diff-config: fix description of diff.renames
2016-04-03 10:29:22 -07:00
Junio C Hamano
11529ecec9 Merge branch 'jk/tighten-alloc'
Update various codepaths to avoid manually-counted malloc().

* jk/tighten-alloc: (22 commits)
  ewah: convert to REALLOC_ARRAY, etc
  convert ewah/bitmap code to use xmalloc
  diff_populate_gitlink: use a strbuf
  transport_anonymize_url: use xstrfmt
  git-compat-util: drop mempcpy compat code
  sequencer: simplify memory allocation of get_message
  test-path-utils: fix normalize_path_copy output buffer size
  fetch-pack: simplify add_sought_entry
  fast-import: simplify allocation in start_packfile
  write_untracked_extension: use FLEX_ALLOC helper
  prepare_{git,shell}_cmd: use argv_array
  use st_add and st_mult for allocation size computation
  convert trivial cases to FLEX_ARRAY macros
  use xmallocz to avoid size arithmetic
  convert trivial cases to ALLOC_ARRAY
  convert manual allocations to argv_array
  argv-array: add detach function
  add helpers for allocating flex-array structs
  harden REALLOC_ARRAY and xcalloc against size_t overflow
  tree-diff: catch integer overflow in combine_diff_path allocation
  ...
2016-02-26 13:37:16 -08:00
Junio C Hamano
3ed26a44b3 Merge branch 'jk/more-comments-on-textconv'
The memory ownership rule of fill_textconv() API, which was a bit
tricky, has been documented a bit better.

* jk/more-comments-on-textconv:
  diff: clarify textconv interface
2016-02-26 13:37:15 -08:00
Matthieu Moy
5404c116aa diff: activate diff.renames by default
Rename detection is a very convenient feature, and new users shouldn't
have to dig in the documentation to benefit from it.

Potential objections to activating rename detection are that it
sometimes fail, and it is sometimes slow. But rename detection is
already activated by default in several cases like "git status" and "git
merge", so activating diff.renames does not fundamentally change the
situation. When the rename detection fails, it now fails consistently
between "git diff" and "git status".

This setting does not affect plumbing commands, hence well-written
scripts will not be affected.

Signed-off-by: Matthieu Moy <Matthieu.Moy@imag.fr>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2016-02-25 11:31:02 -08:00
Jeff King
a64e6a44c6 diff: clarify textconv interface
The memory allocation scheme for the textconv interface is a
bit tricky, and not well documented. It was originally
designed as an internal part of diff.c (matching
fill_mmfile), but gradually was made public.

Refactoring it is difficult, but we can at least improve the
situation by documenting the intended flow and enforcing it
with an in-code assertion.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2016-02-22 10:40:35 -08:00
Jeff King
5b442c4f27 tree-diff: catch integer overflow in combine_diff_path allocation
A combine_diff_path struct has two "flex" members allocated
alongside the struct: a string to hold the pathname, and an
array of parent pointers. We use an "int" to compute this,
meaning we may easily overflow it if the pathname is
extremely long.

We can fix this by using size_t, and checking for overflow
with the st_add helper.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2016-02-19 09:40:37 -08:00
Junio C Hamano
02dab5d399 Merge branch 'nd/diff-with-path-params' into maint
A few options of "git diff" did not work well when the command was
run from a subdirectory.

* nd/diff-with-path-params:
  diff: make -O and --output work in subdirectory
  diff-no-index: do not take a redundant prefix argument
2016-02-05 14:54:15 -08:00
Junio C Hamano
c167a96e68 Merge branch 'nd/diff-with-path-params'
A few options of "git diff" did not work well when the command was
run from a subdirectory.

* nd/diff-with-path-params:
  diff: make -O and --output work in subdirectory
  diff-no-index: do not take a redundant prefix argument
2016-02-03 14:16:04 -08:00
Duy Nguyen
a97262c62f diff: make -O and --output work in subdirectory
Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2016-01-21 10:45:13 -08:00
Nguyễn Thái Ngọc Duy
e5f7a5d16f diff-no-index: do not take a redundant prefix argument
Prefix is already set up in "revs". The same prefix should be used for
all options parsing. So kill the last argument. This patch does not
actually change anything because the only caller does use the same
prefix for init_revisions() and diff_no_index().

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2016-01-21 10:45:11 -08:00
Jeff King
9a93c6686f avoid shifting signed integers 31 bits
We sometimes use 32-bit unsigned integers as bit-fields.
It's fine to access the MSB, because it's unsigned. However,
doing so as "1 << 31" is wrong, because the constant "1" is
a signed int, and we shift into the sign bit, causing
undefined behavior.

We can fix this by using "1U" as the constant.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2016-01-04 09:51:16 -08:00
David Turner
076c98372e log: add "log.follow" configuration variable
People who work on projects with mostly linear history with frequent
whole file renames may want to always use "git log --follow" when
inspecting the life of the content that live in a single path.

Teach the command to behave as if "--follow" was given from the
command line when log.follow configuration variable is set *and*
there is one (and only one) path on the command line.

Signed-off-by: David Turner <dturner@twopensource.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2015-07-09 10:24:23 -07:00
Junio C Hamano
db65170ee5 Merge branch 'jk/color-diff-plain-is-context'
"color.diff.plain" was a misnomer; give it 'color.diff.context' as
a more logical synonym.

* jk/color-diff-plain-is-context:
  diff.h: rename DIFF_PLAIN color slot to DIFF_CONTEXT
  diff: accept color.diff.context as a synonym for "plain"
2015-06-11 09:29:53 -07:00
Junio C Hamano
709cd912d4 Merge branch 'jc/diff-ws-error-highlight'
Allow whitespace breakages in deleted and context lines to be also
painted in the output.

* jc/diff-ws-error-highlight:
  diff.c: --ws-error-highlight=<kind> option
  diff.c: add emit_del_line() and emit_context_line()
  t4015: separate common setup and per-test expectation
  t4015: modernise style
2015-06-11 09:29:51 -07:00
Jeff King
8dbf3eb685 diff.h: rename DIFF_PLAIN color slot to DIFF_CONTEXT
The latter is a much more descriptive name (and we support
"color.diff.context" now). This also updates the name of any
local variables which were used to store the color.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2015-05-27 13:54:42 -07:00
Junio C Hamano
b8767f791c diff.c: --ws-error-highlight=<kind> option
Traditionally, we only cared about whitespace breakages introduced
in new lines.  Some people want to paint whitespace breakages on old
lines, too.  When they see a whitespace breakage on a new line, they
can spot the same kind of whitespace breakage on the corresponding
old line and want to say "Ah, those breakages are there but they
were inherited from the original, so let's not touch them for now."

Introduce `--ws-error-highlight=<kind>` option, that lets them pass
a comma separated list of `old`, `new`, and `context` to specify
what lines to highlight whitespace errors on.

Signed-off-by: Junio C Hamano <gitster@pobox.com>
2015-05-26 23:00:01 -07:00
brian m. carlson
1ff57c13c5 diff: convert struct combine_diff_path to object_id
Also, convert a constant to GIT_SHA1_HEXSZ.

Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2015-03-13 22:43:13 -07:00
Junio C Hamano
8eaf517835 Merge branch 'ks/tree-diff-nway'
Instead of running N pair-wise diff-trees when inspecting a
N-parent merge, find the set of paths that were touched by walking
N+1 trees in parallel.  These set of paths can then be turned into
N pair-wise diff-tree results to be processed through rename
detections and such.  And N=2 case nicely degenerates to the usual
2-way diff-tree, which is very nice.

* ks/tree-diff-nway:
  mingw: activate alloca
  combine-diff: speed it up, by using multiparent diff tree-walker directly
  tree-diff: rework diff_tree() to generate diffs for multiparent cases as well
  Portable alloca for Git
  tree-diff: reuse base str(buf) memory on sub-tree recursion
  tree-diff: no need to call "full" diff_tree_sha1 from show_path()
  tree-diff: rework diff_tree interface to be sha1 based
  tree-diff: diff_tree() should now be static
  tree-diff: remove special-case diff-emitting code for empty-tree cases
  tree-diff: simplify tree_entry_pathcmp
  tree-diff: show_path prototype is not needed anymore
  tree-diff: rename compare_tree_entry -> tree_entry_pathcmp
  tree-diff: move all action-taking code out of compare_tree_entry()
  tree-diff: don't assume compare_tree_entry() returns -1,0,1
  tree-diff: consolidate code for emitting diffs and recursion in one place
  tree-diff: show_tree() is not needed
  tree-diff: no need to pass match to skip_uninteresting()
  tree-diff: no need to manually verify that there is no mode change for a path
  combine-diff: move changed-paths scanning logic into its own function
  combine-diff: move show_log_first logic/action out of paths scanning
2014-06-03 12:06:40 -07:00
Kirill Smelkov
72441af7c4 tree-diff: rework diff_tree() to generate diffs for multiparent cases as well
Previously diff_tree(), which is now named ll_diff_tree_sha1(), was
generating diff_filepair(s) for two trees t1 and t2, and that was
usually used for a commit as t1=HEAD~, and t2=HEAD - i.e. to see changes
a commit introduces.

In Git, however, we have fundamentally built flexibility in that a
commit can have many parents - 1 for a plain commit, 2 for a simple merge,
but also more than 2 for merging several heads at once.

For merges there is a so called combine-diff, which shows diff, a merge
introduces by itself, omitting changes done by any parent. That works
through first finding paths, that are different to all parents, and then
showing generalized diff, with separate columns for +/- for each parent.
The code lives in combine-diff.c .

There is an impedance mismatch, however, in that a commit could
generally have any number of parents, and that while diffing trees, we
divide cases for 2-tree diffs and more-than-2-tree diffs. I mean there
is no special casing for multiple parents commits in e.g.
revision-walker .

That impedance mismatch *hurts* *performance* *badly* for generating
combined diffs - in "combine-diff: optimize combine_diff_path
sets intersection" I've already removed some slowness from it, but from
the timings provided there, it could be seen, that combined diffs still
cost more than an order of magnitude more cpu time, compared to diff for
usual commits, and that would only be an optimistic estimate, if we take
into account that for e.g. linux.git there is only one merge for several
dozens of plain commits.

That slowness comes from the fact that currently, while generating
combined diff, a lot of time is spent computing diff(commit,commit^2)
just to only then intersect that huge diff to almost small set of files
from diff(commit,commit^1).

That's because at present, to compute combine-diff, for first finding
paths, that "every parent touches", we use the following combine-diff
property/definition:

D(A,P1...Pn) = D(A,P1) ^ ... ^ D(A,Pn)      (w.r.t. paths)

where

D(A,P1...Pn) is combined diff between commit A, and parents Pi

and

D(A,Pi) is usual two-tree diff Pi..A

So if any of that D(A,Pi) is huge, tracting 1 n-parent combine-diff as n
1-parent diffs and intersecting results will be slow.

And usually, for linux.git and other topic-based workflows, that
D(A,P2) is huge, because, if merge-base of A and P2, is several dozens
of merges (from A, via first parent) below, that D(A,P2) will be diffing
sum of merges from several subsystems to 1 subsystem.

The solution is to avoid computing n 1-parent diffs, and to find
changed-to-all-parents paths via scanning A's and all Pi's trees
simultaneously, at each step comparing their entries, and based on that
comparison, populate paths result, and deduce we could *skip*
*recursing* into subdirectories, if at least for 1 parent, sha1 of that
dir tree is the same as in A. That would save us from doing significant
amount of needless work.

Such approach is very similar to what diff_tree() does, only there we
deal with scanning only 2 trees simultaneously, and for n+1 tree, the
logic is a bit more complex:

D(T,P1...Pn) calculation scheme
-------------------------------

D(T,P1...Pn) = D(T,P1) ^ ... ^ D(T,Pn)	(regarding resulting paths set)

    D(T,Pj)		- diff between T..Pj
    D(T,P1...Pn)	- combined diff from T to parents P1,...,Pn

We start from all trees, which are sorted, and compare their entries in
lock-step:

     T     P1       Pn
     -     -        -
    |t|   |p1|     |pn|
    |-|   |--| ... |--|      imin = argmin(p1...pn)
    | |   |  |     |  |
    |-|   |--|     |--|
    |.|   |. |     |. |
     .     .        .
     .     .        .

at any time there could be 3 cases:

    1)  t < p[imin];
    2)  t > p[imin];
    3)  t = p[imin].

Schematic deduction of what every case means, and what to do, follows:

1)  t < p[imin]  ->  ∀j t ∉ Pj  ->  "+t" ∈ D(T,Pj)  ->  D += "+t";  t↓

2)  t > p[imin]

    2.1) ∃j: pj > p[imin]  ->  "-p[imin]" ∉ D(T,Pj)  ->  D += ø;  ∀ pi=p[imin]  pi↓
    2.2) ∀i  pi = p[imin]  ->  pi ∉ T  ->  "-pi" ∈ D(T,Pi)  ->  D += "-p[imin]";  ∀i pi↓

3)  t = p[imin]

    3.1) ∃j: pj > p[imin]  ->  "+t" ∈ D(T,Pj)  ->  only pi=p[imin] remains to investigate
    3.2) pi = p[imin]  ->  investigate δ(t,pi)
     |
     |
     v

    3.1+3.2) looking at δ(t,pi) ∀i: pi=p[imin] - if all != ø  ->

                      ⎧δ(t,pi)  - if pi=p[imin]
             ->  D += ⎨
                      ⎩"+t"     - if pi>p[imin]

    in any case t↓  ∀ pi=p[imin]  pi↓

~

For comparison, here is how diff_tree() works:

D(A,B) calculation scheme
-------------------------

    A     B
    -     -
   |a|   |b|    a < b   ->  a ∉ B   ->   D(A,B) +=  +a    a↓
   |-|   |-|    a > b   ->  b ∉ A   ->   D(A,B) +=  -b    b↓
   | |   | |    a = b   ->  investigate δ(a,b)            a↓ b↓
   |-|   |-|
   |.|   |.|
    .     .
    .     .

~~~~~~~~

This patch generalizes diff tree-walker to work with arbitrary number of
parents as described above - i.e. now there is a resulting tree t, and
some parents trees tp[i] i=[0..nparent). The generalization builds on
the fact that usual diff

D(A,B)

is by definition the same as combined diff

D(A,[B]),

so if we could rework the code for common case and make it be not slower
for nparent=1 case, usual diff(t1,t2) generation will not be slower, and
multiparent diff tree-walker would greatly benefit generating
combine-diff.

What we do is as follows:

1) diff tree-walker ll_diff_tree_sha1() is internally reworked to be
   a paths generator (new name diff_tree_paths()), with each generated path
   being `struct combine_diff_path` with info for path, new sha1,mode and for
   every parent which sha1,mode it was in it.

2) From that info, we can still generate usual diff queue with
   struct diff_filepairs, via "exporting" generated
   combine_diff_path, if we know we run for nparent=1 case.
   (see emit_diff() which is now named emit_diff_first_parent_only())

3) In order for diff_can_quit_early(), which checks

       DIFF_OPT_TST(opt, HAS_CHANGES))

   to work, that exporting have to be happening not in bulk, but
   incrementally, one diff path at a time.

   For such consumers, there is a new callback in diff_options
   introduced:

       ->pathchange(opt, struct combine_diff_path *)

   which, if set to !NULL, is called for every generated path.

   (see new compat ll_diff_tree_sha1() wrapper around new paths
    generator for setup)

4) The paths generation itself, is reworked from previous
   ll_diff_tree_sha1() code according to "D(A,P1...Pn) calculation
   scheme" provided above:

   On the start we allocate [nparent] arrays in place what was
   earlier just for one parent tree.

   then we just generalize loops, and comparison according to the
   algorithm.

Some notes(*):

1) alloca(), for small arrays, is used for "runs not slower for
   nparent=1 case than before" goal - if we change it to xmalloc()/free()
   the timings get ~1% worse. For alloca() we use just-introduced
   xalloca/xalloca_free compatibility wrappers, so it should not be a
   portability problem.

2) For every parent tree, we need to keep a tag, whether entry from that
   parent equals to entry from minimal parent. For performance reasons I'm
   keeping that tag in entry's mode field in unused bit - see S_IFXMIN_NEQ.
   Not doing so, we'd need to alloca another [nparent] array, which hurts
   performance.

3) For emitted paths, memory could be reused, if we know the path was
   processed via callback and will not be needed later. We use efficient
   hand-made realloc-style path_appendnew(), that saves us from ~1-1.5%
   of potential additional slowdown.

4) goto(s) are used in several places, as the code executes a little bit
   faster with lowered register pressure.

Also

- we should now check for FIND_COPIES_HARDER not only when two entries
  names are the same, and their hashes are equal, but also for a case,
  when a path was removed from some of all parents having it.

  The reason is, if we don't, that path won't be emitted at all (see
  "a > xi" case), and we'll just skip it, and FIND_COPIES_HARDER wants
  all paths - with diff or without - to be emitted, to be later analyzed
  for being copies sources.

  The new check is only necessary for nparent >1, as for nparent=1 case
  xmin_eqtotal always =1 =nparent, and a path is always added to diff as
  removal.

~~~~~~~~

Timings for

    # without -c, i.e. testing only nparent=1 case
    `git log --raw --no-abbrev --no-renames`

before and after the patch are as follows:

                navy.git        linux.git v3.10..v3.11

    before      0.611s          1.889s
    after       0.619s          1.907s
    slowdown    1.3%            0.9%

This timings show we did no harm to usual diff(tree1,tree2) generation.
From the table we can see that we actually did ~1% slowdown, but I think
I've "earned" that 1% in the previous patch ("tree-diff: reuse base
str(buf) memory on sub-tree recursion", HEAD~~) so for nparent=1 case,
net timings stays approximately the same.

The output also stayed the same.

(*) If we revert 1)-4) to more usual techniques, for nparent=1 case,
    we'll get ~2-2.5% of additional slowdown, which I've tried to avoid, as
   "do no harm for nparent=1 case" rule.

For linux.git, combined diff will run an order of magnitude faster and
appropriate timings will be provided in the next commit, as we'll be
taking advantage of the new diff tree-walker for combined-diff
generation there.

P.S. and combined diff is not some exotic/for-play-only stuff - for
example for a program I write to represent Git archives as readonly
filesystem, there is initial scan with

    `git log --reverse --raw --no-abbrev --no-renames -c`

to extract log of what was created/changed when, as a result building a
map

    {}  sha1    ->  in which commit (and date) a content was added

that `-c` means also show combined diff for merges, and without them, if
a merge is non-trivial (merges changes from two parents with both having
separate changes to a file), or an evil one, the map will not be full,
i.e. some valid sha1 would be absent from it.

That case was my initial motivation for combined diffs speedup.

Signed-off-by: Kirill Smelkov <kirr@mns.spb.ru>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2014-04-07 14:40:46 -07:00
Kirill Smelkov
ad6f3cc7d2 tree-diff: diff_tree() should now be static
We reworked all its users to use the functionality through
diff_tree_sha1 variant in recent patches (see "tree-diff: allow
diff_tree_sha1 to accept NULL sha1" and what comes next).

diff_tree() is now not used outside tree-diff.c - make it static.

Signed-off-by: Kirill Smelkov <kirr@mns.spb.ru>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2014-03-26 14:30:47 -07:00
Junio C Hamano
2687ffdeb7 Merge branch 'jc/hold-diff-remove-q-synonym-for-no-deletion'
Remove a confusing and deprecated "-q" option from "git diff-files";
"git diff-files --diff-filter=d" can be used instead.
2014-03-07 15:17:41 -08:00
Kirill Smelkov
af82c7880f combine-diff: combine_diff_path.len is not needed anymore
The field was used in order to speed-up name comparison and also to
mark removed paths by setting it to 0.

Because the updated code does significantly less strcmp and also
just removes paths from the list and free right after we know a path
will not be needed, it is not needed anymore.

Signed-off-by: Kirill Smelkov <kirr@mns.spb.ru>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2014-02-24 14:44:57 -08:00
Junio C Hamano
73b063130b Merge branch 'tg/diff-no-index-refactor'
"git diff ../else/where/A ../else/where/B" when ../else/where is
clearly outside the repository, and "git diff --no-index A B", do
not have to look at the index at all, but we used to read the index
unconditionally.

* tg/diff-no-index-refactor:
  diff: avoid some nesting
  diff: add test for --no-index executed outside repo
  diff: don't read index when --no-index is given
  diff: move no-index detection to builtin/diff.c
2013-12-27 14:58:17 -08:00
Junio C Hamano
6904f9aa5b Merge branch 'zk/difftool-counts'
Show the total number of paths and the number of paths shown so far
when "git difftool" prompts to launch an external diff tool, which
would give users some sense of progress.

* zk/difftool-counts:
  diff.c: fix some recent whitespace style violations
  difftool: display the number of files in the diff queue in the prompt
2013-12-27 14:58:13 -08:00
Thomas Gummerer
470faf9654 diff: move no-index detection to builtin/diff.c
Currently the --no-index option is parsed in diff_no_index().  Move the
detection if a no-index diff should be executed to builtin/diff.c, where
we can use it for executing diff_no_index() conditionally.  This will
also allow us to execute other operations conditionally, which will be
done in the next patch.

There are no functional changes.

Helped-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Thomas Gummerer <t.gummerer@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2013-12-12 12:23:02 -08:00