Merge branch 'sh/submodule-summary-abbrev-fix'

The "git submodule summary" subcommand showed shortened commit
object names by mechanically truncating them at 7-hexdigit, which
has been improved to let "rev-parse --short" scale the length of
the abbreviation with the size of the repository.

* sh/submodule-summary-abbrev-fix:
  git-submodule.sh: shorten submodule SHA-1s using rev-parse

git-submodule.sh

@@ -850,8 +850,11 @@ cmd_summary() {
 			;;
 		esac
-		sha1_abbr_src=$(echo $sha1_src | cut -c1-7)
-		sha1_abbr_dst=$(echo $sha1_dst | cut -c1-7)
+		sha1_abbr_src=$(GIT_DIR="$name/.git" git rev-parse --short $sha1_src 2>/dev/null ||
+			echo $sha1_src | cut -c1-7)
+		sha1_abbr_dst=$(GIT_DIR="$name/.git" git rev-parse --short $sha1_dst 2>/dev/null ||
+			echo $sha1_dst | cut -c1-7)
+
 		if test $status = T
 		then
 			blob="$(gettext "blob")"