Make: prevent repeating version strings

In the case where the current git HEAD matches the latest release tag,
the version reported by Flamenco was something like
`3.0-beta2-3.0-beta2`, where the first is `$VERSION` and the other is
`$GITHASH`.

This is now prevented, and `$GITHASH` will always be something that's
not a repeat of `$VERSION`.

Makefile

@@ -5,7 +5,18 @@ PKG := git.blender.org/flamenco
 VERSION := 3.0-beta2
 RELEASE_CYCLE := beta
 
-GITHASH := $(subst v${VERSION}-,,$(shell git describe --dirty --always))
+# _GIT_DESCRIPTION_OR_TAG is either something like '16-123abc' (when we're 16
+# commits since the last tag) or it's something like `v3.0-beta2` (when exactly
+# on a tagged version).
+_GIT_DESCRIPTION_OR_TAG := $(subst v${VERSION}-,,$(shell git describe --dirty --always))
+# In the above cases, GITHASH is either `16-123abc` (in the same case above) or
+# `123abc` (when the tag matches the current commit exactly) or `dirty` (when
+# the tag matches the current commit exactly, and there are subsequent
+# uncommitted changes). This is done to prevent repetition of the same tag
+# in the "extended version" of Flamenco, which combines ${VERSION} and
+# ${GITHASH}.
+GITHASH := $(subst v${VERSION},$(shell git rev-parse --short HEAD),${_GIT_DESCRIPTION_OR_TAG})
+
 LDFLAGS := -X ${PKG}/internal/appinfo.ApplicationVersion=${VERSION} \
 	-X ${PKG}/internal/appinfo.ApplicationGitHash=${GITHASH} \
 	-X ${PKG}/internal/appinfo.ReleaseCycle=${RELEASE_CYCLE}