@matheusbsbs / matheus-bagliano / commits / a7256debd4

checkout.txt: note about losing staged changes with --merge

If you have staged changes in path A and perform 'checkout --merge' (which could result in conflicts in a totally unrelated path B), changes in A will be gone. Which is unexpected. We are supposed to keep all changes, or kick and scream otherwise. This is the result of how --merge is implemented, from the very first day in 1be0659efc (checkout: merge local modifications while switching branches., 2006-01-12): 1. a merge is done, unmerged entries are collected 2. a hard switch to a new branch is done, then unmerged entries added back There is no trivial fix for this. Going with 3-way merge one file at a time loses rename detection. Going with 3-way merge by trees requires teaching the algorithm to pick up staged changes. And even if we detect staged changes with --merge and abort for safety, an option to continue --merge is very weird. Such an option would keep worktree changes, but drop staged changes. Because the problem has been with us since the introduction of --merge and everybody has been pretty happy (except Phillip, who found this problem), I'll just take a note here to acknowledge it and wait for merge wizards to come in and work their magic. There may be a way forward [1]. [1] CABPp-BFoL_U=bzON4SEMaQSKU2TKwnOgNqjt5MUaOejTKGUJxw@mail.gmail.com Reported-by: Phillip Wood <phillip.wood@dunelm.org.uk> Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>

Nguyễn Thái Ngọc Duy committed Mar 19, 2019 at 16:39 UTC a7256debd4b6ba9f6ccb94c0958ef48cdd8cb664

2 files changed +11

Documentation/git-checkout.txt

@@ -242,6 +242,8 @@ should result in deletion of the path).

242 +

243 When checking out paths from the index, this option lets you recreate

244 the conflicted merge in the specified paths.

245 ++

246 +When switching branches with `--merge`, staged changes may be lost.

247

248 --conflict=<style>::

249 The same as --merge option above, but changes the way the

builtin/checkout.c

@@ -676,6 +676,8 @@ static int merge_working_tree(const struct checkout_opts *opts,

676 struct tree *result;

677 struct tree *work;

678 struct merge_options o;

679 + struct strbuf sb = STRBUF_INIT;

680 +

681 if (!opts->merge)

682 return 1;

683

@@ -686,6 +688,13 @@ static int merge_working_tree(const struct checkout_opts *opts,

688 if (!old_branch_info->commit)

689 return 1;

690

691 + if (repo_index_has_changes(the_repository,

692 + get_commit_tree(old_branch_info->commit),

693 + &sb))

694 + warning(_("staged changes in the following files may be lost: %s"),

695 + sb.buf);

696 + strbuf_release(&sb);

697 +

698 /* Do more real merge */

699

700 /*