[PATCH v2 1/5] GIT-VERSION-GEN: fix overriding version via environment

From: Patrick Steinhardt <ps@pks.im>
Date: Dec 20, 2024, 12:22 UTC
Message-ID: <20241220-b4-pks-git-version-via-environment-v2-1-f1457a5e8c38@pks.im>
In-Reply-To: <20241220-b4-pks-git-version-via-environment-v2-0-f1457a5e8c38@pks.im>

GIT-VERSION-GEN tries to derive the version that Git is being built from via multiple different sources in the following order:

  1. A file called "version" in the source tree's root directory, if it
     exists.

  2. The current commit in case Git is built from a Git repository.

  3. Otherwise, we use a fallback version stored in a variable which is
     bumped whenever a new Git version is getting tagged.

It used to be possible to override the version by overriding the `GIT_VERSION` Makefile variable (e.g. `make GIT_VERSION=foo`). This worked somewhat by chance, only: `GIT-VERSION-GEN` would write the actual Git version into `GIT-VERSION-FILE`, not the overridden value, but when including the file into our Makefile we would not override the `GIT_VERSION` variable because it has already been set by the user. And because our Makefile used the variable to propagate the version to our build tools instead of using `GIT-VERSION-FILE` the resulting build artifacts used the overridden version.

But that subtle mechanism broke with 4838deab65 (Makefile: refactor GIT-VERSION-GEN to be reusable, 2024-12-06) and subsequent commits because the version information is not propagated via the Makefile variable anymore, but instead via the files that `GIT-VERSION-GEN` started to write. And as the script never knew about the `GIT_VERSION` environment variable in the first place it uses one of the values listed above instead of the overridden value.

Fix this issue by making `GIT-VERSION-GEN` handle the case where `GIT_VERSION` has been set via the environment.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
---
 GIT-VERSION-GEN | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/GIT-VERSION-GEN b/GIT-VERSION-GEN
index de0e63bdfbac263884e2ea328cc2ef11ace7a238..27f9d6a81f77248c652649ae21d0ec51b8f2d247 100755
--- a/GIT-VERSION-GEN
+++ b/GIT-VERSION-GEN
@@ -29,7 +29,10 @@ export GIT_CEILING_DIRECTORIES
 
 # First see if there is a version file (included in release tarballs),
 # then try git-describe, then default.
-if test -f "$SOURCE_DIR"/version
+if test -n "$GIT_VERSION"
+then
+    VN="$GIT_VERSION"
+elif test -f "$SOURCE_DIR"/version
 then
 	VN=$(cat "$SOURCE_DIR"/version) || VN="$DEF_VER"
 elif {
@@ -51,7 +54,13 @@ else
 	VN="$DEF_VER"
 fi
 
-GIT_VERSION=$(expr "$VN" : v*'\(.*\)')
+# Only strip leading `v` in case we have derived VN manually. Otherwise we
+# retain whatever the user has set in their environment.
+if test -z "$GIT_VERSION"
+then
+    GIT_VERSION=$(expr "$VN" : v*'\(.*\)')
+fi
+
 GIT_BUILT_FROM_COMMIT=$(git -C "$SOURCE_DIR" rev-parse -q --verify HEAD 2>/dev/null)
 GIT_DATE=$(git -C "$SOURCE_DIR" show --quiet --format='%as' 2>/dev/null)
 if test -z "$GIT_USER_AGENT"

-- 
2.48.0.rc0.184.g0fc57dec57.dirty