On Fri, Dec 20, 2024 at 10:52:23AM -0500, Jeff King wrote:

On Fri, Dec 20, 2024 at 01:22:45PM +0100, Patrick Steinhardt wrote:

quoted

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

Hmm. If $GIT_VERSION is set, then we set $VN here...

quoted

-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

...but later we ignore $VN completely.

So it would work equally well with the first hunk dropped completely.
However, having an entry in the cascading if/else does mean that we
short-circuit the effort to run git-describe, etc.

I don't think the old code ever did that (we'd generate the Makefile
snippet in GIT-VERSION-FILE, read it back, and then make would still
override the value from the snippet).

So I dunno. I like keeping things simple, but I also like skipping
unnecessary code, too. Maybe if the top hunk were:

  if test -n "$GIT_VERSION"
  then
    : do nothing, we will use this value verbatim
  elif ...

that would make the intended flow more obvious.

There are probably other ways to structure it, too. The whole $VN thing
could be inside the:

  if test -z "$GIT_VERSION"

block. Or alternatively, if each block of the if/else just ran expr and
set $GIT_VERSION itself (perhaps with a one-liner helper function) then
we wouldn't need $VN at all.

I don't know how much trouble it's worth to refactor all this. Mostly I
was just surprised to see the first hunk at all in this version.

I think wrapping it all in `if test -z "$GIT_VERSION"` would be best. I
was thinking about whether to do that refactoring, but I shied away from
it due to the required reindentation. But I agree that the end result is
a bit on the awkward side.

You know, let me send another iteration where I just do it, now that
we're two having the same thought.

Patrick