[PATCH] refuse to merge during a merge

[Clemens Buchacher <drizzd@aon.at>]

The following is an easy mistake to make for users coming from version
control systems with an "update and commit"-style workflow.

        1. git pull
        2. resolve conflicts
        3. git pull

Step 3 overrides MERGE_HEAD, starting a new merge with dirty index.
IOW, probably not what the user intented. Instead, refuse to merge
again if a merge is in progress and present the user with his options.

"git reset --hard" is not suggested, because it potentially removes
changes unrelated to the merge (if the work tree was dirty prior to
the merge).

Reported-by: Dave Olszewski <cxreg@pobox.com>
Signed-off-by: Clemens Buchacher <drizzd@aon.at>
---

Ok, since I'm not seeing any more objections. Here's the code.

Clemens

 builtin-merge.c |   10 ++++++++--
 1 files changed, 8 insertions(+), 2 deletions(-)

diff --git a/builtin-merge.c b/builtin-merge.c
index 0b58e5e..8169ded 100644
--- a/builtin-merge.c
+++ b/builtin-merge.c
@@ -834,10 +834,16 @@ int cmd_merge(int argc, const char **argv, const char *prefix)
 	struct commit_list *common = NULL;
 	const char *best_strategy = NULL, *wt_strategy = NULL;
 	struct commit_list **remotes = &remoteheads;
+	int unmerged;
 
 	setup_work_tree();
-	if (read_cache_unmerged())
-		die("You are in the middle of a conflicted merge.");
+	unmerged = read_cache_unmerged();
+	if (unmerged || file_exists(git_path("MERGE_HEAD")))
+		die("You are in the middle of a %smerge. To complete "
+			"the merge %scommit the changes. To abort, "
+			"use \"git reset HEAD\".",
+			unmerged ? "conflicted " : "",
+			unmerged ? "resolve conflicts and " : "");
 
 	/*
 	 * Check if we are _not_ on a detached HEAD, i.e. if there is a
-- 
1.6.3.1.147.g637c3