git-am --resolved: more usable error message.

After doing the hard work of hand resolving the conflicts in the
working tree, if the user forgets to run update-index to mark
the paths that have been resolved, the command gave an
unfriendly "fatal: git-write-tree: not able to write tree" error
message.  Catch the situation early and give more meaningful
message and suggestion.

Noticed and suggested by Len Brown.

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

diff --git a/git-am.sh b/git-am.sh
index eab4aa8..872145b 100755 (executable)
--- a/git-am.sh
+++ b/git-am.sh
@@ -376,6 +376,13 @@ do
                        echo "No changes - did you forget update-index?"
                        stop_here $this
                fi
+               unmerged=$(git-ls-files -u)
+               if test -n "$unmerged"
+               then
+                       echo "You still have unmerged paths in your index"
+                       echo "did you forget update-index?"
+                       stop_here $this
+               fi
                apply_status=0
                ;;
        esac