version.sh: Print versions based on the last git tag for release branches

release branches are detected by checking if "git" is not in RELEASE
This changes "N-64706-g2f71aeb" to "n2.3-8-g2f71aeb"
for git master theres no change

This should improve the readability of lists of versions which come from
more than 1 release branch or master + release. fate.ffmpeg.org is
one possible example
Reviewed-by: Timothy Gu <timothygu99@gmail.com>
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
(cherry picked from commit ee606fd0317df202b59946cf9b738c0a01056316)
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

version.sh

@@ -4,7 +4,11 @@
 
 # check for git short hash
 if ! test "$revision"; then
-    revision=$(cd "$1" && git describe --tags --match N 2> /dev/null)
+    if (cd "$1" && grep git RELEASE 2> /dev/null >/dev/null) ; then
+        revision=$(cd "$1" && git describe --tags --match N 2> /dev/null)
+    else
+        revision=$(cd "$1" && git describe --tags --always 2> /dev/null)
+    fi
 fi
 
 # Shallow Git clones (--depth) do not have the N tag: