[PATCH] update-index: add --swap to swap index and worktree content

["Nguyễn Thái Ngọc Duy" <pclouds@gmail.com>]

Sometimes "git add -p" with "e" to edit the patch does not satisfy me.
What I want is a quick way to modify index content without changing
worktree, then I can continue adding more hunks to the index.

With this option, I can swap index out for a quick edit, then swap it in
again.

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
---
 Not sure if anybody has the same needs, enough to polish it and make
 it to master.

 builtin/update-index.c |   16 ++++++++++++++++
 1 files changed, 16 insertions(+), 0 deletions(-)

diff --git a/builtin/update-index.c b/builtin/update-index.c
index a6a23fa..b96065a 100644
--- a/builtin/update-index.c
+++ b/builtin/update-index.c
@@ -22,6 +22,7 @@
 static int allow_add;
 static int allow_remove;
 static int allow_replace;
+static int swap_entry;
 static int info_only;
 static int force_remove;
 static int verbose;
@@ -104,6 +105,19 @@ static int add_one_path(struct cache_entry *old, const char *path, int len, stru
 		free(ce);
 		return -1;
 	}
+	if (swap_entry) {
+		struct checkout state;
+		if (allow_add || allow_remove)
+			die("--add, --replace and --swap do not play together");
+		memset(&state, 0, sizeof(state));
+		state.force = 1;
+		state.not_new = 1;
+		if (add_cache_entry(ce, 0))
+			return error("%s: cannot add to the index", path);
+		if (checkout_entry(old, &state, NULL))
+			return error("%s: cannot swap", path);
+		return 0;
+	}
 	option = allow_add ? ADD_CACHE_OK_TO_ADD : 0;
 	option |= allow_replace ? ADD_CACHE_OK_TO_REPLACE : 0;
 	if (add_cache_entry(ce, option))
@@ -727,6 +741,8 @@ int cmd_update_index(int argc, const char **argv, const char *prefix)
 			"let files replace directories and vice-versa", 1),
 		OPT_SET_INT(0, "remove", &allow_remove,
 			"notice files missing from worktree", 1),
+		OPT_SET_INT(0, "swap", &swap_entry,
+			"swap the content of index and worktree", 1),
 		OPT_BIT(0, "unmerged", &refresh_args.flags,
 			"refresh even if index contains unmerged entries",
 			REFRESH_UNMERGED),
-- 
1.7.4.74.g639db