The GIT-VERSION-GEN script computes the version that Git is being built
from. When building from a commit with an unclean worktree it knows to
append "-dirty" to that version to indicate that there were custom
changes applied and that it isn't the exact same as that commit.
The dirtiness check is done manually via git-diff-index(1), which is
somewhat puzzling though: we already use git-describe(1) to compute the
version, which also knows to compute dirtiness via the "--dirty" flag.
But digging back in history explains why: the "-dirty" suffix was added
in 31e0b2ca81 (GIT 1.5.4.3, 2008-02-23), and git-describe(1) didn't yet
have support for "--dirty" back then.
Refactor the script to use git-describe(1). Despite being simpler, it
also results in a small speedup:
Benchmark 1: git describe --dirty --match "v[0-9]*"
Time (mean ± σ): 12.5 ms ± 0.3 ms [User: 6.3 ms, System: 8.8 ms]
Range (min … max): 12.0 ms … 13.5 ms 200 runs
Benchmark 2: git describe --match "v[0-9]*" HEAD && git update-index -q --refresh && git diff-index --name-only HEAD --
Time (mean ± σ): 17.9 ms ± 1.1 ms [User: 8.8 ms, System: 14.4 ms]
Range (min … max): 17.0 ms … 30.6 ms 148 runs
Summary
git describe --dirty --match "v[0-9]*" ran
1.43 ± 0.09 times faster than git describe --match "v[0-9]*" && git update-index -q --refresh && git diff-index --name-only HEAD --
While the speedup doesn't really matter on Unix-based systems, where
filesystem operations are typically fast, they do matter on Windows
where the commands take a couple hundred milliseconds. A quick and dirty
check on that system shows a speedup from ~800ms to ~400ms.
Signed-off-by: Patrick Steinhardt <ps@xxxxxx>
---
GIT-VERSION-GEN | 6 +-----
1 file changed, 1 insertion(+), 5 deletions(-)
diff --git a/GIT-VERSION-GEN b/GIT-VERSION-GEN
index f2af817feaeb384dee0ffd197f02a31cf2d31f87..754b8ca9eedaa2f7e3b61c83c1cc763538394fe6 100755
--- a/GIT-VERSION-GEN
+++ b/GIT-VERSION-GEN
@@ -39,13 +39,9 @@ then
test -d "${GIT_DIR:-.git}" ||
test -f "$SOURCE_DIR"/.git;
} &&
- VN=$(git -C "$SOURCE_DIR" describe --match "v[0-9]*" HEAD 2>/dev/null) &&
+ VN=$(git -C "$SOURCE_DIR" describe --match --dirty "v[0-9]*" 2>/dev/null) &&
case "$VN" in
*$LF*) (exit 1) ;;
- v[0-9]*)
- git -C "$SOURCE_DIR" update-index -q --refresh
- test -z "$(git -C "$SOURCE_DIR" diff-index --name-only HEAD --)" ||
- VN="$VN-dirty" ;;
esac
then
VN=$(echo "$VN" | sed -e 's/-/./g');
--
2.48.0.257.gd3603152ad.dirty
