Re: fatal: git-write-tree: not able to write tree

"Brown, Len" [off-list ref] writes about the command "git
am -3 --resolved", after hand merging _but_ without update-index
to actually mark the paths that have been resolved, results in
"write-tree" failure.

I'm okay with git being conservative and not doing the update-index
for me.  Perhaps the thing to do here is to make the failure message
more useful?

"fatal: git-write-tree: not able to write tree"

everything after "fatal" here is effectively a string
of random characters to the hapless user.

That's very true.  Perhaps something like this?

-- >8 --
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 <redacted>
---

diff --git a/git-am.sh b/git-am.sh
index eab4aa8..872145b 100755
--- 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