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diff: don't read index when --no-index is given 

git diff --no-index ... currently reads the index, during setup, when
calling gitmodules_config().  This results in worse performance when the
index is not actually needed.  This patch avoids calling
gitmodules_config() when the --no-index option is given.  The times for
executing "git diff --no-index" in the WebKit repository are improved as
follows:

Test                      HEAD~3            HEAD
------------------------------------------------------------------
4001.1: diff --no-index   0.24(0.15+0.09)   0.01(0.00+0.00) -95.8%

An additional improvement of this patch is that "git diff --no-index" no
longer breaks when the index file is corrupt, which makes it possible to
use it for investigating the broken repository.

To improve the possible usage as investigation tool for broken
repositories, setup_git_directory_gently() is also not called when the
--no-index option is given.

Also add a test to guard against future breakages, and a performance
test to show the improvements.

Signed-off-by: Thomas Gummerer <t.gummerer@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This commit is contained in:
Thomas Gummerer 2013-12-11 10:58:43 +01:00 committed by Junio C Hamano
parent 470faf9654
commit 6df5762db3
3 changed files with 42 additions and 2 deletions
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7
builtin/diff.c
View File

@ -298,7 +298,9 @@ int cmd_diff(int argc, const char **argv, const char *prefix)
break;
}
prefix = setup_git_directory_gently(&nongit);
if (!no_index)
prefix = setup_git_directory_gently(&nongit);
/*
* Treat git diff with at least one path outside of the
* repo the same as if the command would have been executed
@ -311,7 +313,8 @@ int cmd_diff(int argc, const char **argv, const char *prefix)
!path_inside_repo(prefix, argv[i + 1]))))
no_index = DIFF_NO_INDEX_IMPLICIT;
gitmodules_config();
if (!no_index)
gitmodules_config();
git_config(git_diff_ui_config, NULL);
init_revisions(&rev, prefix);

22
t/perf/p4001-diff-no-index.sh Executable file
View File

@ -0,0 +1,22 @@
#!/bin/sh
test_description="Test diff --no-index performance"
. ./perf-lib.sh
test_perf_large_repo
test_checkout_worktree
file1=$(git ls-files | tail -n 2 | head -1)
file2=$(git ls-files | tail -n 1 | head -1)
test_expect_success "empty files, so they take no time to diff" "
echo >$file1 &&
echo >$file2
"
test_perf "diff --no-index" "
git diff --no-index $file1 $file2 >/dev/null
"
test_done

15
t/t4053-diff-no-index.sh
View File

@ -29,4 +29,19 @@ test_expect_success 'git diff --no-index relative path outside repo' '
)
'
test_expect_success 'git diff --no-index with broken index' '
(
cd repo &&
echo broken >.git/index &&
git diff --no-index a ../non/git/a
)
'
test_expect_success 'git diff outside repo with broken index' '
(
cd repo &&
git diff ../non/git/a ../non/git/b
)
'
test_done