[Mesa-dev] [PATCH 2/2] automake: bring back the .PHONY git_sha1.h.tmp rule

[Emil Velikov]

From: Emil Velikov <emil.velikov at collabora.com>

With earlier commit 3689ef32afd ("automake: rework the git_sha1.h rule,
include in tarball") we/I erroneously removed the PHONY rule and the
temporary file.

The former is used to ensure that the header is regenerated when on each
make invocation, while the latter helps us avoid the unneeded rebuild(s)
when the SHA1 hasn't changed.

Cc: Grazvydas Ignotas <notasas at gmail.com>
Reported-by: Grazvydas Ignotas <notasas at gmail.com>
Signed-off-by: Emil Velikov <emil.l.velikov at gmail.com>
---
And the brown paper bag for "keep one change per commit" goes to yours
truly... Grazvydas can you give it a test on your end ?
---
 src/Makefile.am | 19 +++++++++++++++++--
 1 file changed, 17 insertions(+), 2 deletions(-)

diff --git a/src/Makefile.am b/src/Makefile.am
index f5c0773..45590c0 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -19,13 +19,28 @@
 # FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
 # IN THE SOFTWARE.
 
-git_sha1.h:
+.PHONY: git_sha1.h.tmp
+git_sha1.h.tmp:
+	@# Don't assume that $(top_srcdir)/.git is a directory. It may be
+	@# a gitlink file if $(top_srcdir) is a submodule checkout or a linked
+	@# worktree.
+	@# If we are building from a release tarball copy the bundled header.
 	@if test -e $(top_srcdir)/.git; then \
 		if which git > /dev/null; then \
 		    git --git-dir=$(top_srcdir)/.git log -n 1 --oneline | \
 			sed 's/^\([^ ]*\) .*/#define MESA_GIT_SHA1 "git-\1"/' \
-			> git_sha1.h ; \
+			> git_sha1.h.tmp ; \
 		fi \
+	else \
+		cp git_sha1.h git_sha1.h.tmp ;\
+	fi
+
+git_sha1.h: git_sha1.h.tmp
+	@echo "updating git_sha1.h"
+	@if ! cmp -s git_sha1.h.tmp git_sha1.h; then \
+		mv git_sha1.h.tmp git_sha1.h ;\
+	else \
+		rm git_sha1.h.tmp ;\
 	fi
 
 BUILT_SOURCES = git_sha1.h
-- 
2.8.2