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[PATCH 1/2] shortlog: introduce `--group-filter` to restrict output

From
Taylor Blau <me@ttaylorr.com>
Date
Jun 7, 2023, 23:02 UTC
Message-ID
<5cec04b65d350ca8b482ca14260ef118341e4039.1686178917.git.me@ttaylorr.com>
In-Reply-To
<cover.1686178917.git.me@ttaylorr.com>

Sometimes it is useful to ask, "how many commits have I authored or been mentioned in via the Co-authored-by trailer"? `git shortlog` is a reasonable tool for this, and the answer can easily be obtained by running:

    $ git shortlog -ns --group=author --group=trailer:Co-authored-by

and reading off the corresponding value from its output. But what if you want to know which commits contribute to the above count? You can drop the `-s` option and parse through the results, but you'll have to skip past everything you don't want (and stop reading after matching everything you do want).

That is a script-able task, but it is cumbersome, and potentially very slow, if there is a large amount of output that does not match the given query.

Instead, this patch introduces `--group-filter` in order to restrict the output of `git shortlog` to only matching group(s). Items match if they are in a group which is strictly equal to one of the specified filters.

This means that you could easily view the hashes of all commits you either wrote or co-authored with something like:

    $ git shortlog -n --group=author --group=trailer:Co-authored-by \
        --group-filter="$(git config user.name)"

When filtering just by trailers, it is tempting to want to introduce a new grep mode for matching a given trailer, like `--author=<pattern>` for matching the author header. But this would not be suitable for the above, since we want commits which match either the author or the Co-authored-by trailer, not ones which match both.

An alternative approach might be to implement trailer filtering as above in revision.c, and show commits matching either the `--author` value or some hypothetical `--trailer` filter. That would give shortlog fewer commits, which may improve its performance. But it would restrict the interpretation of these options to be an OR (i.e. show commits matching either the `--author` or `--trailer` field).

In fact, this is already not possible to do, since the `--author` and `--committer` options are documented as:

> Limit the commits output to ones with author/committer header lines
> that match the specified pattern

So introducing another option which changes the behavior of existing ones is a non-starter.

Instead, `git shortlog` will process more commits than necessary. But this is a marginal cost, since implementing the hypothetical revision options from above as an OR would mean that revision.c has to process every commit anyway.

Signed-off-by: Taylor Blau <me@ttaylorr.com>
---
 Documentation/git-shortlog.txt |  5 ++++
 builtin/shortlog.c             | 20 ++++++++++++-
 shortlog.h                     |  2 ++
 t/t4201-shortlog.sh            | 54 ++++++++++++++++++++++++++++++++++
 4 files changed, 80 insertions(+), 1 deletion(-)
diff --git a/Documentation/git-shortlog.txt b/Documentation/git-shortlog.txt
index 7d0277d033..dab6d09648 100644
--- a/Documentation/git-shortlog.txt
+++ b/Documentation/git-shortlog.txt
@@ -97,6 +97,11 @@ counts both authors and co-authors.
 If width is `0` (zero) then indent the lines of the output without wrapping
 them.
 
+--group-filter=<group>::
+	Only show output from the given group. If given more than once,
+	show output from any of the previously specified groups. May be
+	cleared with `--no-group-filter`.
+
 <revision-range>::
 	Show only commits in the specified revision range.  When no
 	<revision-range> is specified, it defaults to `HEAD` (i.e. the
diff --git a/builtin/shortlog.c b/builtin/shortlog.c
index 46f4e0832a..679db22c57 100644
--- a/builtin/shortlog.c
+++ b/builtin/shortlog.c
@@ -365,6 +365,7 @@ void shortlog_init(struct shortlog *log)
 	log->trailers.strdup_strings = 1;
 	log->trailers.cmp = strcasecmp;
 	log->format.strdup_strings = 1;
+	log->group_filter.strdup_strings = 1;
 }
 
 void shortlog_finish_setup(struct shortlog *log)
@@ -377,6 +378,7 @@ void shortlog_finish_setup(struct shortlog *log)
 				   log->email ? "%cN <%cE>" : "%cN");
 
 	string_list_sort(&log->trailers);
+	string_list_sort(&log->group_filter);
 }
 
 int cmd_shortlog(int argc, const char **argv, const char *prefix)
@@ -400,6 +402,8 @@ int cmd_shortlog(int argc, const char **argv, const char *prefix)
 			&parse_wrap_args),
 		OPT_CALLBACK(0, "group", &log, N_("field"),
 			N_("group by field"), parse_group_option),
+		OPT_STRING_LIST(0, "group-filter", &log.group_filter,
+				N_("group"), N_("only show matching groups")),
 		OPT_END(),
 	};
 
@@ -476,6 +480,13 @@ static void add_wrapped_shortlog_msg(struct strbuf *sb, const char *s,
 	strbuf_addch(sb, '\n');
 }
 
+static int want_shortlog_group(struct shortlog *log, const char *group)
+{
+	if (!log->group_filter.nr)
+		return 1;
+	return string_list_has_string(&log->group_filter, group);
+}
+
 void shortlog_output(struct shortlog *log)
 {
 	size_t i, j;
@@ -486,6 +497,9 @@ void shortlog_output(struct shortlog *log)
 		      log->summary ? compare_by_counter : compare_by_list);
 	for (i = 0; i < log->list.nr; i++) {
 		const struct string_list_item *item = &log->list.items[i];
+		if (!want_shortlog_group(log, item->string))
+			goto next;
+
 		if (log->summary) {
 			fprintf(log->file, "%6d\t%s\n",
 				(int)UTIL_TO_INT(item), item->string);
@@ -505,11 +519,15 @@ void shortlog_output(struct shortlog *log)
 					fprintf(log->file, "      %s\n", msg);
 			}
 			putc('\n', log->file);
+		}
+
+next:
+		if (!log->summary) {
+			struct string_list *onelines = item->util;
 			onelines->strdup_strings = 1;
 			string_list_clear(onelines, 0);
 			free(onelines);
 		}
-
 		log->list.items[i].util = NULL;
 	}
 
diff --git a/shortlog.h b/shortlog.h
index 28d04f951a..8ebee0e2d6 100644
--- a/shortlog.h
+++ b/shortlog.h
@@ -18,6 +18,8 @@ struct shortlog {
 	int abbrev;
 	struct date_mode date_mode;
 
+	struct string_list group_filter;
+
 	enum {
 		SHORTLOG_GROUP_AUTHOR = (1 << 0),
 		SHORTLOG_GROUP_COMMITTER = (1 << 1),
diff --git a/t/t4201-shortlog.sh b/t/t4201-shortlog.sh
index 8e4effebdb..0695c42ca8 100755
--- a/t/t4201-shortlog.sh
+++ b/t/t4201-shortlog.sh
@@ -346,6 +346,60 @@ test_expect_success 'shortlog can match multiple groups' '
 	test_cmp expect actual
 '
 
+test_expect_success '--group-filter shows only matching groups (single groups)' '
+	cat >expect <<-\EOF &&
+	     1	A U Thor
+	EOF
+	git shortlog -ns \
+		--group=trailer:another-trailer \
+		--group-filter="A U Thor" \
+		-2 HEAD >actual &&
+	test_cmp expect actual
+'
+
+test_expect_success '--group-filter shows only matching groups (multiple groups)' '
+	cat >expect <<-\EOF &&
+	     2	A U Thor
+	EOF
+	git shortlog -ns \
+		--group=author \
+		--group=trailer:some-trailer \
+		--group=trailer:another-trailer \
+		--group-filter="A U Thor" \
+		-2 HEAD >actual &&
+	test_cmp expect actual
+'
+
+test_expect_success '--group-filter can be specified more than once' '
+	cat >expect <<-\EOF &&
+	     2	User B
+	     1	User A
+	EOF
+	git shortlog -ns \
+		--group=author \
+		--group=trailer:some-trailer \
+		--group=trailer:another-trailer \
+		--group-filter="User A" \
+		--group-filter="User B" \
+		-2 HEAD >actual &&
+	test_cmp expect actual
+'
+
+test_expect_success '--no-group-filter reset group filters' '
+	cat >expect <<-\EOF &&
+	     2	A U Thor
+	     2	User B
+	     1	User A
+	EOF
+	git shortlog -ns \
+		--group=author \
+		--group=trailer:some-trailer \
+		--group=trailer:another-trailer \
+		--group-filter="A U Thor" --no-group-filter \
+		-2 HEAD >actual &&
+	test_cmp expect actual
+'
+
 test_expect_success 'shortlog can match multiple format groups' '
 	GIT_COMMITTER_NAME="$GIT_AUTHOR_NAME" \
 		git commit --allow-empty -m "identical names" &&

-- 
2.41.0.1.gf123b68cb8
Previous: Taylor BlauNext: Derrick Stolee
Message 2 of 8 in “shortlog: introduce --email-only, --group-filter options”
  1. 0/2 shortlog: introduce --email-only, --group-filter optionsTaylor Blau, Jun 7, 2023
  2. 1/2 shortlog: introduce `--group-filter` to restrict outputTaylor Blau, Jun 7, 2023
  3. Derrick StoleeJun 8, 2023
  4. Taylor BlauJun 8, 2023
  5. 2/2 shortlog: introduce `--email-only` to only show emailsTaylor Blau, Jun 7, 2023
  6. Johannes SixtJun 8, 2023
  7. Taylor BlauJun 8, 2023
  8. Junio C HamanoJun 12, 2023

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