[PATCH 3/3] reset: Print a warning when user uses "git reset" during a merge

[Andrew Wong <andrew.kw.w@gmail.com>]

During a merge, "--mixed" is most likely not what the user wants. Using
"--mixed" during a merge would leave the merged changes and new files
mixed in with the local changes. The user would have to manually clean
up the work tree, which is non-trivial. In future releases, we want to
make "git reset" error out when used in the middle of a merge. For now,
we simply print out a warning to the user.

Signed-off-by: Andrew Wong <andrew.kw.w@gmail.com>
---
 builtin/reset.c | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/builtin/reset.c b/builtin/reset.c
index 4fd1c6c..04e8103 100644
--- a/builtin/reset.c
+++ b/builtin/reset.c
@@ -331,8 +331,29 @@ int cmd_reset(int argc, const char **argv, const char *prefix)
 					_(reset_type_names[reset_type]));
 	}
 	if (reset_type == NONE)
+	{
 		reset_type = MIXED; /* by default */
 
+		/* During a merge, "--mixed" is most likely not what the user
+		 * wants. Using "--mixed" during a merge would leave the merged
+		 * changes and new files mixed in with the local changes. The
+		 * user would have to manually clean up the work tree, which is
+		 * non-trivial. In future releases, we want to make "git reset"
+		 * error out when used in the middle of a merge. For now, we
+		 * simply print out a warning to the user. */
+		if (is_merge())
+			warning(_("You have used 'git reset' in the middle of a merge. 'git reset' defaults to\n"
+				  "'git reset --mixed', which means git will not clean up any merged changes and\n"
+				  "new files that were created in the work tree. It also becomes impossible for\n"
+				  "git to automatically clean up the work tree later, so you would have to clean\n"
+				  "up the work tree manually. To avoid this next time, you may want to use 'git\n"
+				  "reset --merge', or equivalently 'git merge --abort'.\n"
+				  "\n"
+				  "In future releases, using 'git reset' in the middle of a merge will result in\n"
+				  "an error."
+				 ));
+	}
+
 	if (reset_type != SOFT && reset_type != MIXED)
 		setup_work_tree();
 
-- 
1.9.0.174.g6f75b8f