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sequencer: introduce the merge command

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This patch is part of the effort to reimplement `--preserve-merges` with
a substantially improved design, a design that has been developed in the
Git for Windows project to maintain the dozens of Windows-specific patch
series on top of upstream Git.

The previous patch implemented the `label` and `reset` commands to label
commits and to reset to labeled commits. This patch adds the `merge`
command, with the following syntax:

	merge [-C <commit>] <rev> # <oneline>

The <commit> parameter in this instance is the *original* merge commit,
whose author and message will be used for the merge commit that is about
to be created.

The <rev> parameter refers to the (possibly rewritten) revision to
merge. Let's see an example of a todo list (the initial `label onto`
command is an auto-generated convenience so that the label `onto` can be
used to refer to the revision onto which we rebase):

	label onto

	# Branch abc
	reset onto
	pick deadbeef Hello, world!
	label abc

	reset onto
	pick cafecafe And now for something completely different
	merge -C baaabaaa abc # Merge the branch 'abc' into master

To edit the merge commit's message (a "reword" for merges, if you will),
use `-c` (lower-case) instead of `-C`; this convention was borrowed from
`git commit` that also supports `-c` and `-C` with similar meanings.

To create *new* merges, i.e. without copying the commit message from an
existing commit, simply omit the `-C <commit>` parameter (which will
open an editor for the merge message):

	merge abc

This comes in handy when splitting a branch into two or more branches.

Note: this patch only adds support for recursive merges, to keep things
simple. Support for octopus merges will be added later in a separate
patch series, support for merges using strategies other than the
recursive merge is left for the future.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This commit is contained in:
Johannes Schindelin 2018-04-25 14:28:54 +02:00 committed by Junio C Hamano
parent 9055e401dd
commit 4c68e7ddb5
2 changed files with 204 additions and 0 deletions
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4
git-rebase--interactive.sh
View File

@ -164,6 +164,10 @@ x, exec <commit> = run command (the rest of the line) using shell
d, drop <commit> = remove commit
l, label <label> = label current HEAD with a name
t, reset <label> = reset HEAD to a label
m, merge [-C <commit> | -c <commit>] <label> [# <oneline>]
. create a merge commit using the original merge commit's
. message (or the oneline, if no original merge commit was
. specified). Use -c <commit> to reword the commit message.
These lines can be re-ordered; they are executed from top to bottom.
" | git stripspace --comment-lines >>"$todo"

200
sequencer.c
View File

@ -1307,6 +1307,7 @@ enum todo_command {
TODO_EXEC,
TODO_LABEL,
TODO_RESET,
TODO_MERGE,
/* commands that do nothing but are counted for reporting progress */
TODO_NOOP,
TODO_DROP,
@ -1327,6 +1328,7 @@ static struct {
{ 'x', "exec" },
{ 'l', "label" },
{ 't', "reset" },
{ 'm', "merge" },
{ 0, "noop" },
{ 'd', "drop" },
{ 0, NULL }
@ -1754,9 +1756,14 @@ static int read_and_refresh_cache(struct replay_opts *opts)
return 0;
}
enum todo_item_flags {
TODO_EDIT_MERGE_MSG = 1
};
struct todo_item {
enum todo_command command;
struct commit *commit;
unsigned int flags;
const char *arg;
int arg_len;
size_t offset_in_buf;
@ -1791,6 +1798,8 @@ static int parse_insn_line(struct todo_item *item, const char *bol, char *eol)
char *end_of_object_name;
int i, saved, status, padding;
item->flags = 0;
/* left-trim */
bol += strspn(bol, " \t");
@ -1840,6 +1849,21 @@ static int parse_insn_line(struct todo_item *item, const char *bol, char *eol)
return 0;
}
if (item->command == TODO_MERGE) {
if (skip_prefix(bol, "-C", &bol))
bol += strspn(bol, " \t");
else if (skip_prefix(bol, "-c", &bol)) {
bol += strspn(bol, " \t");
item->flags |= TODO_EDIT_MERGE_MSG;
} else {
item->flags |= TODO_EDIT_MERGE_MSG;
item->commit = NULL;
item->arg = bol;
item->arg_len = (int)(eol - bol);
return 0;
}
}
end_of_object_name = (char *) bol + strcspn(bol, " \t\n");
saved = *end_of_object_name;
*end_of_object_name = '\0';
@ -2654,6 +2678,158 @@ static int do_reset(const char *name, int len, struct replay_opts *opts)
return ret;
}
static int do_merge(struct commit *commit, const char *arg, int arg_len,
int flags, struct replay_opts *opts)
{
int run_commit_flags = (flags & TODO_EDIT_MERGE_MSG) ?
EDIT_MSG | VERIFY_MSG : 0;
struct strbuf ref_name = STRBUF_INIT;
struct commit *head_commit, *merge_commit, *i;
struct commit_list *bases, *j, *reversed = NULL;
struct merge_options o;
int merge_arg_len, oneline_offset, ret;
static struct lock_file lock;
const char *p;
if (hold_locked_index(&lock, LOCK_REPORT_ON_ERROR) < 0) {
ret = -1;
goto leave_merge;
}
head_commit = lookup_commit_reference_by_name("HEAD");
if (!head_commit) {
ret = error(_("cannot merge without a current revision"));
goto leave_merge;
}
oneline_offset = arg_len;
merge_arg_len = strcspn(arg, " \t\n");
p = arg + merge_arg_len;
p += strspn(p, " \t\n");
if (*p == '#' && (!p[1] || isspace(p[1]))) {
p += 1 + strspn(p + 1, " \t\n");
oneline_offset = p - arg;
} else if (p - arg < arg_len)
BUG("octopus merges are not supported yet: '%s'", p);
strbuf_addf(&ref_name, "refs/rewritten/%.*s", merge_arg_len, arg);
merge_commit = lookup_commit_reference_by_name(ref_name.buf);
if (!merge_commit) {
/* fall back to non-rewritten ref or commit */
strbuf_splice(&ref_name, 0, strlen("refs/rewritten/"), "", 0);
merge_commit = lookup_commit_reference_by_name(ref_name.buf);
}
if (!merge_commit) {
ret = error(_("could not resolve '%s'"), ref_name.buf);
goto leave_merge;
}
if (commit) {
const char *message = get_commit_buffer(commit, NULL);
const char *body;
int len;
if (!message) {
ret = error(_("could not get commit message of '%s'"),
oid_to_hex(&commit->object.oid));
goto leave_merge;
}
write_author_script(message);
find_commit_subject(message, &body);
len = strlen(body);
ret = write_message(body, len, git_path_merge_msg(), 0);
unuse_commit_buffer(commit, message);
if (ret) {
error_errno(_("could not write '%s'"),
git_path_merge_msg());
goto leave_merge;
}
} else {
struct strbuf buf = STRBUF_INIT;
int len;
strbuf_addf(&buf, "author %s", git_author_info(0));
write_author_script(buf.buf);
strbuf_reset(&buf);
if (oneline_offset < arg_len) {
p = arg + oneline_offset;
len = arg_len - oneline_offset;
} else {
strbuf_addf(&buf, "Merge branch '%.*s'",
merge_arg_len, arg);
p = buf.buf;
len = buf.len;
}
ret = write_message(p, len, git_path_merge_msg(), 0);
strbuf_release(&buf);
if (ret) {
error_errno(_("could not write '%s'"),
git_path_merge_msg());
goto leave_merge;
}
}
write_message(oid_to_hex(&merge_commit->object.oid), GIT_SHA1_HEXSZ,
git_path_merge_head(), 0);
write_message("no-ff", 5, git_path_merge_mode(), 0);
bases = get_merge_bases(head_commit, merge_commit);
for (j = bases; j; j = j->next)
commit_list_insert(j->item, &reversed);
free_commit_list(bases);
read_cache();
init_merge_options(&o);
o.branch1 = "HEAD";
o.branch2 = ref_name.buf;
o.buffer_output = 2;
ret = merge_recursive(&o, head_commit, merge_commit, reversed, &i);
if (ret <= 0)
fputs(o.obuf.buf, stdout);
strbuf_release(&o.obuf);
if (ret < 0) {
error(_("could not even attempt to merge '%.*s'"),
merge_arg_len, arg);
goto leave_merge;
}
/*
* The return value of merge_recursive() is 1 on clean, and 0 on
* unclean merge.
*
* Let's reverse that, so that do_merge() returns 0 upon success and
* 1 upon failed merge (keeping the return value -1 for the cases where
* we will want to reschedule the `merge` command).
*/
ret = !ret;
if (active_cache_changed &&
write_locked_index(&the_index, &lock, COMMIT_LOCK)) {
ret = error(_("merge: Unable to write new index file"));
goto leave_merge;
}
rollback_lock_file(&lock);
if (ret)
rerere(opts->allow_rerere_auto);
else
/*
* In case of problems, we now want to return a positive
* value (a negative one would indicate that the `merge`
* command needs to be rescheduled).
*/
ret = !!run_git_commit(git_path_merge_msg(), opts,
run_commit_flags);
leave_merge:
strbuf_release(&ref_name);
rollback_lock_file(&lock);
return ret;
}
static int is_final_fixup(struct todo_list *todo_list)
{
int i = todo_list->current;
@ -2860,6 +3036,17 @@ static int pick_commits(struct todo_list *todo_list, struct replay_opts *opts)
} else if (item->command == TODO_RESET) {
if ((res = do_reset(item->arg, item->arg_len, opts)))
reschedule = 1;
} else if (item->command == TODO_MERGE) {
if ((res = do_merge(item->commit,
item->arg, item->arg_len,
item->flags, opts)) < 0)
reschedule = 1;
else if (res > 0)
/* failed with merge conflicts */
return error_with_patch(item->commit,
item->arg,
item->arg_len, opts,
res, 0);
} else if (!is_noop(item->command))
return error(_("unknown command %d"), item->command);
@ -2871,6 +3058,11 @@ static int pick_commits(struct todo_list *todo_list, struct replay_opts *opts)
todo_list->current--;
if (save_todo(todo_list, opts))
return -1;
if (item->commit)
return error_with_patch(item->commit,
item->arg,
item->arg_len, opts,
res, 0);
}
todo_list->current++;
@ -3356,8 +3548,16 @@ int transform_todos(unsigned flags)
short_commit_name(item->commit) :
oid_to_hex(&item->commit->object.oid);
if (item->command == TODO_MERGE) {
if (item->flags & TODO_EDIT_MERGE_MSG)
strbuf_addstr(&buf, " -c");
else
strbuf_addstr(&buf, " -C");
}
strbuf_addf(&buf, " %s", oid);
}
/* add all the rest */
if (!item->arg_len)
strbuf_addch(&buf, '\n');