version.sh: handle shallow clones and snapshots.

Shallow clones (--depth X) lack the N tag used to compute
the revision number: use 'git-YYYY-MM-DD-hhhhhhh' as revision,
where hhhhhhh is the short git hash.

Snapshots from gitweb do not have git information at all,
but they have the short git hash in the directory name:
append it to the release number.

version.sh

@@ -5,9 +5,29 @@ if ! test "$revision"; then
     revision=$(cd "$1" && git describe --tags --match N 2> /dev/null)
 fi
 
+# Shallow Git clones (--depth) do not have the N tag:
+# use 'git-YYYY-MM-DD-hhhhhhh'.
+test "$revision" || revision=$(cd "$1" &&
+  git log -1 --pretty=format:"git-%cd-%h" --date=short 2> /dev/null)
+
+# Snapshots from gitweb are in a directory called ffmpeg-hhhhhhh or
+# ffmpeg-HEAD-hhhhhhh.
+if [ -z "$revision" ]; then
+  srcdir=$(cd "$1" && pwd)
+  case "$srcdir" in
+    */ffmpeg-[0-9a-f][0-9a-f][0-9a-f][0-9a-f][0-9a-f][0-9a-f][0-9a-f])
+      git_hash="${srcdir##*-}";;
+    */ffmpeg-HEAD-[0-9a-f][0-9a-f][0-9a-f][0-9a-f][0-9a-f][0-9a-f][0-9a-f])
+      git_hash="${srcdir##*-}";;
+  esac
+fi
+
 # no revision number found
 test "$revision" || revision=$(cd "$1" && cat RELEASE 2> /dev/null)
 
+# Append the Git hash if we have one
+test "$revision" && test "$git_hash" && revision="$revision-$git_hash"
+
 # releases extract the version number from the VERSION file
 version=$(cd "$1" && cat VERSION 2> /dev/null)
 test "$version" || version=$revision