Ever since commit 3f213981e4 ("add tests for rebasing merged history",
2013-06-06), t3425 has had tests which included the rebasing of merged
history and whose order of applied commits was checked. Unfortunately,
the tests expected different behavior depending on which backend was in
use. Implementing these checks was the following four lines (including
the TODO message) which were repeated verbatim three times in t3425:
#TODO: make order consistent across all flavors of rebase
test_run_rebase success 'e n o' ''
test_run_rebase success 'e n o' -m
test_run_rebase success 'n o e' -i
As part of the effort to reduce differences between the rebase backends
so that users get more uniform behavior, let's define the correct
behavior and modify the different backends so they all get the right
answer. It turns out that the difference in behavior here is entirely
due to topological sorting; since some backends require topological
sorting (particularly when --rebase-merges is specified), require it for
all modes. Modify the am and merge backends to implement this.
Performance Considerations:
I was unable to measure any appreciable performance difference with this
change. Trying to control the run-to-run variation was difficult; I
eventually found a headless beefy box that I could ssh into, which
seemed to help. Using git.git, I ran the following testcase:
$ git reset --hard v2.20.0-rc1~2
$ time git rebase --quiet v2.20.0-rc0~16
I first ran once to warm any disk caches, then ran five subsequent runs
and recorded the times of those five. I observed the following results
for the average time:
Before this change:
"real" timing: 1.340s (standard deviation: 0.040s)
"user" timing: 1.050s (standard deviation: 0.041s)
"sys" timing: 0.270s (standard deviation: 0.011s)
After this change:
"real" timing: 1.327s (standard deviation: 0.065s)
"user" timing: 1.031s (standard deviation: 0.061s)
"sys" timing: 0.280s (standard deviation: 0.014s)
Measurements aside, I would expect the timing for walking revisions to
be dwarfed by the work involved in creating and applying patches, so
this isn't too surprising. Further, while somewhat counter-intuitive,
it is possible that turning on topological sorting is actually a
performance improvement: by way of comparison, turning on --topo-order
made fast-export faster (see
https://public-inbox.org/git/20090211135640.GA19600@coredump.intra.peff.net/).
Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
The `--preserve-merges` mode of the `rebase` command is slated to be
deprecated soon, as the more powerful `--rebase-merges` mode is
available now, and the latter was designed with the express intent to
address the shortcomings of `--preserve-merges`' design (e.g. the
inability to reorder commits in an interactive rebase).
As such, we will eventually even remove the `--preserve-merges` support,
and along with it, its tests.
In preparation for this, and also to allow the Windows phase of our
automated tests to save some well-needed time when running the test
suite, this commit introduces a new prerequisite REBASE_P, which can be
forced to being unmet by setting the environment variable
`GIT_TEST_SKIP_REBASE_P` to any non-empty string.
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
These are tests which are missing a link in their &&-chain,
but during a setup phase. We may fail to notice failure in
commands that build the test environment, but these are
typically not expected to fail at all (but it's still good
to double-check that our test environment is what we
expect).
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
The recently introduced tests used uppercase letters to denote
cherry-picks of commits having the corresponding lowercase letter names.
The helper functions also set up tags with the names of the commits.
But this constellation fails on case-insensitive file systems because
there cannot be distinct tags with names that differ only in case.
Use a less subtle convention for the names of cherry-picked commits.
Signed-off-by: Johannes Sixt <j6t@kdbg.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
