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Provide 'git merge --abort' as a synonym to 'git reset --merge'

Teach 'git merge' the --abort option, which verifies the existence of
MERGE_HEAD and then invokes 'git reset --merge' to abort the current
in-progress merge and attempt to reconstruct the pre-merge state.

The reason for adding this option is to provide a user interface for
aborting an in-progress merge that is consistent with the interface
for aborting a rebase ('git rebase --abort'), aborting the application
of a patch series ('git am --abort'), and aborting an in-progress notes
merge ('git notes merge --abort').

The patch includes documentation and testcases that explain and verify
the various scenarios in which 'git merge --abort' can run. The
testcases also document the cases in which 'git merge --abort' is
unable to correctly restore the pre-merge state (look for the '###'
comments towards the bottom of t/t7609-merge-abort.sh).

This patch has been improved by the following contributions:
- Jonathan Nieder: Move test documentation into test_description

Thanks-to: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Johan Herland <johan@herland.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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1 parent 2a22c1b commit 35d2fffdb857836cc46f5a4ada525a246ddd5e11 @jherland jherland committed with gitster Nov 9, 2010
Showing with 351 additions and 3 deletions.
  1. +24 −3 Documentation/git-merge.txt
  2. +14 −0 builtin/merge.c
  3. +313 −0 t/t7609-merge-abort.sh
@@ -13,6 +13,7 @@ SYNOPSIS
[-s <strategy>] [-X <strategy-option>]
[--[no-]rerere-autoupdate] [-m <msg>] <commit>...
'git merge' <msg> HEAD <commit>...
+'git merge' --abort
DESCRIPTION
-----------
@@ -47,6 +48,14 @@ The second syntax (<msg> `HEAD` <commit>...) is supported for
historical reasons. Do not use it from the command line or in
new scripts. It is the same as `git merge -m <msg> <commit>...`.
+The third syntax ("`git merge --abort`") can only be run after the
+merge has resulted in conflicts. 'git merge --abort' will abort the
+merge process and try to reconstruct the pre-merge state. However,
+if there were uncommitted changes when the merge started (and
+especially if those changes were further modified after the merge
+was started), 'git merge --abort' will in some cases be unable to
+reconstruct the original (pre-merge) changes. Therefore:
+
*Warning*: Running 'git merge' with uncommitted changes is
discouraged: while possible, it leaves you in a state that is hard to
back out of in the case of a conflict.
@@ -72,6 +81,18 @@ include::merge-options.txt[]
Allow the rerere mechanism to update the index with the
result of auto-conflict resolution if possible.
+--abort::
+ Abort the current conflict resolution process, and
+ try to reconstruct the pre-merge state.
++
+If there were uncommitted worktree changes present when the merge
+started, 'git merge --abort' will in some cases be unable to
+reconstruct these changes. It is therefore recommended to always
+commit or stash your changes before running 'git merge'.
++
+'git merge --abort' is equivalent to 'git reset --merge' when
+`MERGE_HEAD` is present.
+
<commit>...::
Commits, usually other branch heads, to merge into our branch.
You need at least one <commit>. Specifying more than one
@@ -142,7 +163,7 @@ happens:
i.e. matching `HEAD`.
If you tried a merge which resulted in complex conflicts and
-want to start over, you can recover with `git reset --merge`.
+want to start over, you can recover with `git merge --abort`.
HOW CONFLICTS ARE PRESENTED
---------------------------
@@ -213,8 +234,8 @@ After seeing a conflict, you can do two things:
* Decide not to merge. The only clean-ups you need are to reset
the index file to the `HEAD` commit to reverse 2. and to clean
- up working tree changes made by 2. and 3.; `git-reset --hard` can
- be used for this.
+ up working tree changes made by 2. and 3.; `git merge --abort`
+ can be used for this.
* Resolve the conflicts. Git will mark the conflicts in
the working tree. Edit the files into shape and
View
@@ -56,6 +56,7 @@ static size_t xopts_nr, xopts_alloc;
static const char *branch;
static int verbosity;
static int allow_rerere_auto;
+static int abort_current_merge;
static struct strategy all_strategy[] = {
{ "recursive", DEFAULT_TWOHEAD | NO_TRIVIAL },
@@ -194,6 +195,8 @@ static struct option builtin_merge_options[] = {
"message to be used for the merge commit (if any)",
option_parse_message),
OPT__VERBOSITY(&verbosity),
+ OPT_BOOLEAN(0, "abort", &abort_current_merge,
+ "abort the current in-progress merge"),
OPT_END()
};
@@ -914,6 +917,17 @@ int cmd_merge(int argc, const char **argv, const char *prefix)
argc = parse_options(argc, argv, prefix, builtin_merge_options,
builtin_merge_usage, 0);
+ if (abort_current_merge) {
+ int nargc = 2;
+ const char *nargv[] = {"reset", "--merge", NULL};
+
+ if (!file_exists(git_path("MERGE_HEAD")))
+ die("There is no merge to abort (MERGE_HEAD missing).");
+
+ /* Invoke 'git reset --merge' */
+ return cmd_reset(nargc, nargv, prefix);
+ }
+
if (read_cache_unmerged())
die_resolve_conflict("merge");
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