Allow GIT version to be used in pacman builds

Add a new configure flag, --enable-git-version, that allows the output of
'git describe' to be used in the version string associated with this
package. This could aid in debugging for users that are using a development
version of pacman and we should be able to figure out which cut of code they
are using.

Sample output:
$ pacman --version
Pacman v3.1.4-190-g4cfa-dirty - libalpm v2.3.1

$ makepkg --version
makepkg (pacman) 3.1.4-190-g5861-dirty

Signed-off-by: Dan McGee <dan@archlinux.org>

1 files changed, 8 insertions, 1 deletions

diff --git a/scripts/Makefile.am b/scripts/Makefile.am
index 3185a476..e6c051b0 100644
--- a/scripts/Makefile.am
+++ b/scripts/Makefile.am
@@ -18,13 +18,20 @@ EXTRA_DIST = \
 # Files that should be removed, but which Automake does not know.
 MOSTLYCLEANFILES = $(bin_SCRIPTS) *.tmp
 
+if USE_GIT_VERSION
+GIT_VERSION := $(shell sh -c 'git describe --abbrev=4 | sed s/^v//')-dirty
+REAL_PACKAGE_VERSION = $(GIT_VERSION)
+else
+REAL_PACKAGE_VERSION = $(PACKAGE_VERSION)
+endif
+
 #### Taken from the autoconf scripts Makefile.am ####
 edit = sed \
 	-e 's|@localedir[@]|$(localedir)|g' \
 	-e 's|@sysconfdir[@]|$(sysconfdir)|g' \
 	-e 's|@localstatedir[@]|$(localstatedir)|g' \
 	-e 's|@prefix[@]|$(prefix)|g' \
-	-e 's|@PACKAGE_VERSION[@]|$(PACKAGE_VERSION)|g' \
+	-e 's|@PACKAGE_VERSION[@]|$(REAL_PACKAGE_VERSION)|g' \
 	-e 's|@PACKAGE_BUGREPORT[@]|$(PACKAGE_BUGREPORT)|g' \
 	-e 's|@PACKAGE_NAME[@]|$(PACKAGE_NAME)|g' \
 	-e 's|@DBEXT[@]|$(DBEXT)|g' \