[PATCH] Allow "+remote:local" refspec to cause --force when fetching.

With this we could say:

    Pull: master:ko-master +pu:ko-pu

to mean "fast forward ko-master with master, overwrite ko-pu with pu",
and the latter one does not require the remote "pu" to be descendant
of local "ko-pu".

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

git-fetch-script

@@ -104,8 +104,8 @@ fast_forward_local () {
 		;;
 	    esac || {
 		echo >&2 "* $1: does not fast forward to $4"
-		case "$force" in
-		t)
+		case "$force,$single_force" in
+		t,* | *,t)
 			echo >&2 "  from $3; forcing update."
 			;;
 		*)
@@ -130,6 +130,13 @@ do
 
     # These are relative path from $GIT_DIR, typically starting at refs/
     # but may be HEAD
+    if expr "$ref" : '\+' >/dev/null
+    then
+	single_force=t
+	ref=$(expr "$ref" : '\+\(.*\)')
+    else
+	single_force=
+    fi
     remote_name=$(expr "$ref" : '\([^:]*\):')
     local_name=$(expr "$ref" : '[^:]*:\(.*\)')
 
@@ -175,9 +182,14 @@ http://* | https://* | rsync://* )
     while read sha1 remote_name
     do
 	found=
+	single_force=
 	for ref in $refs
 	do
 	    case "$ref" in
+	    +$remote_name:*)
+		single_force=t
+		found="$ref"
+		break ;;
 	    $remote_name:*)
 		found="$ref"
 		break ;;

git-parse-remote-script

@@ -69,6 +69,13 @@ get_remote_default_refs_for_push () {
 canon_refs_list_for_fetch () {
 	for ref
 	do
+		force=
+		case "$ref" in
+		+*)
+			ref=$(expr "$ref" : '\+\(.*\)')
+			force=+
+			;;
+		esac
 		expr "$ref" : '.*:' >/dev/null || ref="${ref}:"
 		remote=$(expr "$ref" : '\([^:]*\):')
 		local=$(expr "$ref" : '[^:]*:\(.*\)')
@@ -80,7 +87,7 @@ canon_refs_list_for_fetch () {
 		'') local= ;;
 		*) local="refs/heads/$local" ;;
 		esac
-		echo "${remote}:${local}"
+		echo "${force}${remote}:${local}"
 	done
 }