Allow git-merge not to commit.

Martin Langhoff wants to use git-merge from outside git-pull and wants
to do further processing; for this, he wants git-merge no to commit
even when it cleanly merges.  I think other script writers would want
something like that as well, so here it is.

Instead of the "merge commit message" parameter (which usually is made
for you by "git-pull" which calls this command), you pass an empty
string to it.  Then it will not update your HEAD -- you can do whatever
you want with the resulting index file, which contains the merge results.

Signed-off-by: Junio C Hamano <junkio@cox.net>

diff --git a/git-merge.sh b/git-merge.sh
index 3465041..3457a96 100755 (executable)
--- a/git-merge.sh
+++ b/git-merge.sh
@@ -38,10 +38,20 @@ restorestate() {
        fi
 }
 
-summary() {
+finish () {
+       test '' = "$2" || echo "$2"
+       case "$merge_msg" in
+       '')
+               echo "No merge message -- not updating HEAD"
+               ;;
+       *)
+               git-update-ref HEAD "$1" "$head" || exit 1
+               ;;
+       esac
+
        case "$no_summary" in
        '')
-               git-diff-tree -p -M $head "$1" |
+               git-diff-tree -p -M "$head" "$1" |
                git-apply --stat --summary
                ;;
        esac
@@ -108,7 +118,7 @@ case "$#,$common" in
 1,"$1")
        # If head can reach all the merge then we are up to date.
        # but first the most common case of merging one remote
-       echo "Already up-to-date. Yeeah!"
+       echo "Already up-to-date."
        dropsave
        exit 0
        ;;
@@ -116,10 +126,9 @@ case "$#,$common" in
        # Again the most common case of merging one remote.
        echo "Updating from $head to $1."
        git-update-index --refresh 2>/dev/null
-       git-read-tree -u -m $head "$1" &&
        new_head=$(git-rev-parse --verify "$1^0") &&
-       git-update-ref HEAD "$new_head" "$head" || exit 1
-       summary "$1"
+       git-read-tree -u -m $head "$new_head" &&
+       finish "$new_head" "Fast forward"
        dropsave
        exit 0
        ;;
@@ -140,8 +149,7 @@ case "$#,$common" in
                echo "$merge_msg" |
                git-commit-tree $result_tree -p HEAD -p "$1"
            ) || exit
-           git-update-ref HEAD $result_commit $head
-           summary $result_commit
+           finish "$result_commit" "In-index merge"
            dropsave
            exit 0
        fi
@@ -237,9 +245,7 @@ then
         parents="$parents -p $remote"
     done
     result_commit=$(echo "$merge_msg" | git-commit-tree $result_tree $parents) || exit
-    echo "Committed merge $result_commit, made by $wt_strategy."
-    git-update-ref HEAD $result_commit $head
-    summary $result_commit
+    finish "$result_commit" "Merge $result_commit, made by $wt_strategy."
     dropsave
     exit 0
 fi