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merge-tree: add new --quiet option #1920

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4757c48
merge-ort: add a new mergeability_only option
newren May 8, 2025
7c40d3c
merge-tree: add a new --quiet flag
newren May 8, 2025
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6 changes: 6 additions & 0 deletions Documentation/git-merge-tree.adoc
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Original file line number Diff line number Diff line change
Expand Up @@ -65,6 +65,12 @@ OPTIONS
default is to include these messages if there are merge
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On the Git mailing list, "Kristoffer Haugsbakk" wrote (reply to this):

On Fri, May 16, 2025, at 22:04, Elijah Newren via GitGitGadget wrote:
> From: Elijah Newren <[email protected]>
> +	if (quiet && o.show_messages == -1)
> +		o.show_messages = 0;
> +	o.merge_options.mergeability_only = quiet;
> +	die_for_incompatible_opt2(quiet, "--quiet", o.show_messages, "--messages");
> +	die_for_incompatible_opt2(quiet, "--quiet", o.name_only, "--name-only");
> +	die_for_incompatible_opt2(quiet, "--quiet", o.use_stdin, "--stdin");
> +	die_for_incompatible_opt2(quiet, "--quiet", !line_termination, "-z");

I’ve been using git-merge-tree(1) for some scripting but only today
tried out `--stdin` for printing refs that conflict.

```
# Pipe in pairs
merge_pairs=$(mktemp)
tee $merge_pairs \
    | git merge-tree --stdin --no-messages \
    | tr '\0' '\n' \
    | grep --extended-regexp '^(1|0)$' \
    | paste -d' ' - $merge_pairs \
    | grep '^0' \
    | cut -d' ' -f2-
```

(Previously I called the command in a loop)

I could imagine a `--format` option to just keep one of the arguments,
which means the tee(1) (for cross-referencing the ref) and all the other
things are gone:

```
git merge-tree --format='%(if)%(conflicted)%(then)oid2%(end)' --stdin
```

(But imagined options aside)

`--stdin` is presumably for efficiency and `--quiet`/`--dry-run`
definitely is.  But `--quiet` can only be used in the mode where you can
only do a single merge, not in the `--stdin` batch mode.

`--quiet`/`--dry-run` with informational output (c.f. the above
die-for-incompatible) would “break” the documented output format since
conflicts haven’t been computed all the way and there are no OIDs for
successful merges.  But the user is opting into a new mode here, never
seen before.  Can’t they opt into a new informational mode where
`--stdin --quiet` can co-exist?  Then you can have dry-run batch mode.

-- 
Kristoffer Haugsbakk

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On the Git mailing list, "Kristoffer Haugsbakk" wrote (reply to this):

On Sat, May 17, 2025, at 21:52, Kristoffer Haugsbakk wrote:
> Can’t they opt into a new informational mode where
> `--stdin --quiet` can co-exist?

Yes, I now immediately see the contradiction in the
literal text: “informational mode” and `--quiet`. 
But I shall not weigh in on the naming matter.

-- 
Kristoffer Haugsbakk

conflicts, and to omit them otherwise.

--quiet::
Disable all output from the program. Useful when you are only
interested in the exit status. Allows merge-tree to exit
early when it finds a conflict, and allows it to avoid writing
most objects created by merges.

--allow-unrelated-histories::
merge-tree will by default error out if the two branches specified
share no common history. This flag can be given to override that
Expand Down
18 changes: 18 additions & 0 deletions builtin/merge-tree.c
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Original file line number Diff line number Diff line change
Expand Up @@ -490,6 +490,9 @@ static int real_merge(struct merge_tree_options *o,
if (result.clean < 0)
die(_("failure to merge"));

if (o->merge_options.mergeability_only)
goto cleanup;

if (show_messages == -1)
show_messages = !result.clean;

Expand Down Expand Up @@ -522,6 +525,8 @@ static int real_merge(struct merge_tree_options *o,
}
if (o->use_stdin)
putchar(line_termination);

cleanup:
merge_finalize(&opt, &result);
clear_merge_options(&opt);
return !result.clean; /* result.clean < 0 handled above */
Expand All @@ -538,6 +543,7 @@ int cmd_merge_tree(int argc,
int original_argc;
const char *merge_base = NULL;
int ret;
int quiet = 0;

const char * const merge_tree_usage[] = {
N_("git merge-tree [--write-tree] [<options>] <branch1> <branch2>"),
Expand All @@ -552,6 +558,10 @@ int cmd_merge_tree(int argc,
N_("do a trivial merge only"), MODE_TRIVIAL),
OPT_BOOL(0, "messages", &o.show_messages,
N_("also show informational/conflict messages")),
OPT_BOOL_F(0, "quiet",
&quiet,
N_("suppress all output; only exit status wanted"),
PARSE_OPT_NONEG),
OPT_SET_INT('z', NULL, &line_termination,
N_("separate paths with the NUL character"), '\0'),
OPT_BOOL_F(0, "name-only",
Expand Down Expand Up @@ -583,6 +593,14 @@ int cmd_merge_tree(int argc,
argc = parse_options(argc, argv, prefix, mt_options,
merge_tree_usage, PARSE_OPT_STOP_AT_NON_OPTION);

if (quiet && o.show_messages == -1)
o.show_messages = 0;
o.merge_options.mergeability_only = quiet;
die_for_incompatible_opt2(quiet, "--quiet", o.show_messages, "--messages");
die_for_incompatible_opt2(quiet, "--quiet", o.name_only, "--name-only");
die_for_incompatible_opt2(quiet, "--quiet", o.use_stdin, "--stdin");
die_for_incompatible_opt2(quiet, "--quiet", !line_termination, "-z");

if (xopts.nr && o.mode == MODE_TRIVIAL)
die(_("--trivial-merge is incompatible with all other options"));
for (size_t x = 0; x < xopts.nr; x++)
Expand Down
38 changes: 31 additions & 7 deletions merge-ort.c
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Original file line number Diff line number Diff line change
Expand Up @@ -2127,6 +2127,7 @@ static int handle_content_merge(struct merge_options *opt,
const struct version_info *b,
const char *pathnames[3],
const int extra_marker_size,
const int record_object,
struct version_info *result)
{
/*
Expand Down Expand Up @@ -2214,7 +2215,7 @@ static int handle_content_merge(struct merge_options *opt,
ret = -1;
}

if (!ret &&
if (!ret && record_object &&
write_object_file(result_buf.ptr, result_buf.size,
OBJ_BLOB, &result->oid)) {
path_msg(opt, ERROR_OBJECT_WRITE_FAILED, 0,
Expand Down Expand Up @@ -2897,6 +2898,7 @@ static int process_renames(struct merge_options *opt,
struct version_info merged;
struct conflict_info *base, *side1, *side2;
unsigned was_binary_blob = 0;
const int record_object = true;

pathnames[0] = oldpath;
pathnames[1] = newpath;
Expand Down Expand Up @@ -2947,6 +2949,7 @@ static int process_renames(struct merge_options *opt,
&side2->stages[2],
pathnames,
1 + 2 * opt->priv->call_depth,
record_object,
&merged);
if (clean_merge < 0)
return -1;
Expand Down Expand Up @@ -3061,6 +3064,7 @@ static int process_renames(struct merge_options *opt,

struct conflict_info *base, *side1, *side2;
int clean;
const int record_object = true;

pathnames[0] = oldpath;
pathnames[other_source_index] = oldpath;
Expand All @@ -3080,6 +3084,7 @@ static int process_renames(struct merge_options *opt,
&side2->stages[2],
pathnames,
1 + 2 * opt->priv->call_depth,
record_object,
&merged);
if (clean < 0)
return -1;
Expand Down Expand Up @@ -3931,9 +3936,12 @@ static int write_completed_directory(struct merge_options *opt,
* Write out the tree to the git object directory, and also
* record the mode and oid in dir_info->result.
*/
int record_tree = (!opt->mergeability_only ||
opt->priv->call_depth);
dir_info->is_null = 0;
dir_info->result.mode = S_IFDIR;
if (write_tree(&dir_info->result.oid, &info->versions, offset,
if (record_tree &&
write_tree(&dir_info->result.oid, &info->versions, offset,
opt->repo->hash_algo->rawsz) < 0)
ret = -1;
}
Expand Down Expand Up @@ -4231,10 +4239,13 @@ static int process_entry(struct merge_options *opt,
struct version_info *o = &ci->stages[0];
struct version_info *a = &ci->stages[1];
struct version_info *b = &ci->stages[2];
int record_object = (!opt->mergeability_only ||
opt->priv->call_depth);

clean_merge = handle_content_merge(opt, path, o, a, b,
ci->pathnames,
opt->priv->call_depth * 2,
record_object,
&merged_file);
if (clean_merge < 0)
return -1;
Expand Down Expand Up @@ -4395,6 +4406,8 @@ static int process_entries(struct merge_options *opt,
STRING_LIST_INIT_NODUP,
NULL, 0 };
int ret = 0;
const int record_tree = (!opt->mergeability_only ||
opt->priv->call_depth);

trace2_region_enter("merge", "process_entries setup", opt->repo);
if (strmap_empty(&opt->priv->paths)) {
Expand Down Expand Up @@ -4454,6 +4467,12 @@ static int process_entries(struct merge_options *opt,
ret = -1;
goto cleanup;
};
if (!ci->merged.clean && opt->mergeability_only &&
!opt->priv->call_depth) {
ret = 0;
goto cleanup;
}

}
}
trace2_region_leave("merge", "processing", opt->repo);
Expand All @@ -4468,7 +4487,8 @@ static int process_entries(struct merge_options *opt,
fflush(stdout);
BUG("dir_metadata accounting completely off; shouldn't happen");
}
if (write_tree(result_oid, &dir_metadata.versions, 0,
if (record_tree &&
write_tree(result_oid, &dir_metadata.versions, 0,
opt->repo->hash_algo->rawsz) < 0)
ret = -1;
cleanup:
Expand Down Expand Up @@ -4715,6 +4735,8 @@ void merge_display_update_messages(struct merge_options *opt,

if (opt->record_conflict_msgs_as_headers)
BUG("Either display conflict messages or record them as headers, not both");
if (opt->mergeability_only)
BUG("Displaying conflict messages incompatible with mergeability-only checks");

trace2_region_enter("merge", "display messages", opt->repo);

Expand Down Expand Up @@ -5171,10 +5193,12 @@ static void merge_ort_nonrecursive_internal(struct merge_options *opt,
result->path_messages = &opt->priv->conflicts;

if (result->clean >= 0) {
result->tree = parse_tree_indirect(&working_tree_oid);
if (!result->tree)
die(_("unable to read tree (%s)"),
oid_to_hex(&working_tree_oid));
if (!opt->mergeability_only) {
result->tree = parse_tree_indirect(&working_tree_oid);
if (!result->tree)
die(_("unable to read tree (%s)"),
oid_to_hex(&working_tree_oid));
}
/* existence of conflicted entries implies unclean */
result->clean &= strmap_empty(&opt->priv->conflicted);
}
Expand Down
1 change: 1 addition & 0 deletions merge-ort.h
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Original file line number Diff line number Diff line change
Expand Up @@ -83,6 +83,7 @@ struct merge_options {
/* miscellaneous control options */
const char *subtree_shift;
unsigned renormalize : 1;
unsigned mergeability_only : 1; /* exit early, write fewer objects */
unsigned record_conflict_msgs_as_headers : 1;
const char *msg_header_prefix;

Expand Down
38 changes: 38 additions & 0 deletions t/t4301-merge-tree-write-tree.sh
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Original file line number Diff line number Diff line change
Expand Up @@ -54,6 +54,25 @@ test_expect_success setup '
git commit -m first-commit
'

test_expect_success '--quiet on clean merge' '
# Get rid of loose objects to start with
git gc &&
echo "0 objects, 0 kilobytes" >expect &&
git count-objects >actual &&
test_cmp expect actual &&

# Ensure merge is successful (exit code of 0)
git merge-tree --write-tree --quiet side1 side3 >output &&

# Ensure there is no output
test_must_be_empty output &&

# Ensure no loose objects written (all new objects written would have
# been in "outer layer" of the merge)
git count-objects >actual &&
test_cmp expect actual
'

test_expect_success 'Clean merge' '
TREE_OID=$(git merge-tree --write-tree side1 side3) &&
q_to_tab <<-EOF >expect &&
Expand All @@ -72,6 +91,25 @@ test_expect_success 'Failed merge without rename detection' '
grep "CONFLICT (modify/delete): numbers deleted" out
'

test_expect_success '--quiet on conflicted merge' '
# Get rid of loose objects to start with
git gc &&
echo "0 objects, 0 kilobytes" >expect &&
git count-objects >actual &&
test_cmp expect actual &&

# Ensure merge has conflict
test_expect_code 1 git merge-tree --write-tree --quiet side1 side2 >output &&

# Ensure there is no output
test_must_be_empty output &&

# Ensure no loose objects written (all new objects written would have
# been in "outer layer" of the merge)
git count-objects >actual &&
test_cmp expect actual
'

test_expect_success 'Content merge and a few conflicts' '
git checkout side1^0 &&
test_must_fail git merge side2 &&
Expand Down
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