Make got log -s display commit timestamps in YYYY-MM-DD format,
and display reference names instead of an abbreviated hash if
the reference is a local branch or a tag.

Before:

$ got log -s -l5
6ec249e remove outdated and overly-specific documentation of got log -s output
b58982a adjust expected test output after got log -s changes
92d06b6 make got log -s show committer date
598bd2c make got log -s display local reference names
3ef807e reword description of how got log -p and -P interact with got log -S

After:

$ got log -s -l5
2022-06-11 log-s   remove outdated and overly-specific documentation of got log -s output
2022-06-11 b58982a adjust expected test output after got log -s changes
2022-06-11 92d06b6 make got log -s show committer date
2022-06-11 598bd2c make got log -s display local reference names
2022-06-08 main    reword description of how got log -p and -P interact with got log -S

I believe showing the date is important because commit hashes by themselves
provide no indication of timeline at all. Dates make log -s a lot more useful.

Showing branch names and tags is more readable than always showing
hashes. With longer branch names the log message gets indented a
bit further, but that is no big deal. I chose to omit remote refs
because they cause more indentation and are not always interesting.

I considered adding author info as well but decided against it.
Lines printed by log -s are already too long on small terminals.

I also considered truncating the log message to terminal size but this
is impossible to do correctly without converting to wide characters to
find split-points in UTF-8 byte strings. Since tog already covers this
for people who care about such optics, log -s can stay simple.

Instead of documenting the output changes, just remove overly specific
documentation so we don't have to worry about keeping it up-to-date.

ok?

diff refs/heads/main refs/heads/log-s
blob - 7825117a1854a2737ac5b841f83716ac3749d20a
blob + 769726c3e688f4817f2a83df5beae11d34ea8948
--- got/got.1
+++ got/got.1
@@ -821,8 +821,6 @@ option.
 .It Fl s
 Display a short one-line summary of each commit, instead of the default
 history format.
-The one-line format prints the beginning of the SHA1 hash of each commit,
-followed by a space and the first line of the log message.
 Cannot be used together with the
 .Fl p
 or
blob - 28ba9a46f202c773426d431a909c5dec6304d3ca
blob + 4e1ffc4ac48138e3b509a39589e7d444b9957ab8
--- got/got.c
+++ got/got.c
@@ -3814,7 +3814,8 @@ done:
 
 static const struct got_error*
 build_refs_str(char **refs_str, struct got_reflist_head *refs,
-    struct got_object_id *id, struct got_repository *repo)
+    struct got_object_id *id, struct got_repository *repo,
+    int local_only)
 {
 	static const struct got_error *err = NULL;
 	struct got_reflist_entry *re;
@@ -3838,6 +3839,8 @@ build_refs_str(char **refs_str, struct got_reflist_hea
 		if (strncmp(name, "heads/", 6) == 0)
 			name += 6;
 		if (strncmp(name, "remotes/", 8) == 0) {
+			if (local_only)
+				continue;
 			name += 8;
 			s = strstr(name, "/" GOT_REF_HEAD);
 			if (s != NULL && s[strlen(s)] == '\0')
@@ -3880,15 +3883,40 @@ build_refs_str(char **refs_str, struct got_reflist_hea
 }
 
 static const struct got_error *
-print_commit_oneline(struct got_commit_object *commit, struct got_object_id *id)
+print_commit_oneline(struct got_commit_object *commit, struct got_object_id *id,
+    struct got_repository *repo, struct got_reflist_object_id_map *refs_idmap)
 {
 	const struct got_error *err = NULL;
-	char *id_str, *s, *nl, *logmsg0;
+	char *ref_str = NULL, *id_str = NULL, *logmsg0 = NULL;
+	char *comma, *s, *nl;
+	struct got_reflist_head *refs;
+	char datebuf[12]; /* YYYY-MM-DD + SPACE + NUL */
+	struct tm tm;
+	time_t committer_time;
 
-	err = got_object_id_str(&id_str, id);
-	if (err)
-		return err;
+	refs = got_reflist_object_id_map_lookup(refs_idmap, id);
+	if (refs) {
+		err = build_refs_str(&ref_str, refs, id, repo, 1);
+		if (err)
+			goto done;
 
+		/* Display the first matching ref only. */
+		if (ref_str && (comma = strchr(ref_str, ',')) != NULL)
+			*comma = '\0';
+	}
+
+	if (ref_str == NULL) {
+		err = got_object_id_str(&id_str, id);
+		if (err)
+			return err;
+	}
+
+	committer_time = got_object_commit_get_committer_time(commit);
+	if (gmtime_r(&committer_time, &tm) == NULL)
+		return got_error_from_errno("gmtime_r");
+	if (strftime(datebuf, sizeof(datebuf), "%G-%m-%d ", &tm) == 0)
+		return got_error(GOT_ERR_NO_SPACE);
+
 	err = got_object_commit_get_logmsg(&logmsg0, commit);
 	if (err)
 		goto done;
@@ -3902,12 +3930,16 @@ print_commit_oneline(struct got_commit_object *commit,
 		*nl = '\0';
 	}
 
-	printf("%.7s %s\n", id_str, s);
+	if (ref_str)
+		printf("%s%-7s %s\n", datebuf, ref_str, s);
+	else
+		printf("%s%.7s %s\n", datebuf, id_str, s);
 
 	if (fflush(stdout) != 0 && err == NULL)
 		err = got_error_from_errno("fflush");
 done:
 	free(id_str);
+	free(ref_str);
 	free(logmsg0);
 	return err;
 }
@@ -3934,7 +3966,7 @@ print_commit(struct got_commit_object *commit, struct 
 		struct got_reflist_head *refs;
 		refs = got_reflist_object_id_map_lookup(refs_idmap, id);
 		if (refs) {
-			err = build_refs_str(&refs_str, refs, id, repo);
+			err = build_refs_str(&refs_str, refs, id, repo, 0);
 			if (err)
 				goto done;
 		}
@@ -4101,7 +4133,8 @@ print_commits(struct got_object_id *root_id, struct go
 			got_object_commit_close(commit);
 		} else {
 			if (one_line)
-				err = print_commit_oneline(commit, id);
+				err = print_commit_oneline(commit, id,
+				    repo, refs_idmap);
 			else
 				err = print_commit(commit, id, repo, path,
 				    show_changed_paths ? &changed_paths : NULL,
@@ -4133,7 +4166,8 @@ print_commits(struct got_object_id *root_id, struct go
 					break;
 			}
 			if (one_line)
-				err = print_commit_oneline(commit, &qid->id);
+				err = print_commit_oneline(commit, &qid->id,
+				    repo, refs_idmap);
 			else
 				err = print_commit(commit, &qid->id, repo, path,
 				    show_changed_paths ? &changed_paths : NULL,
@@ -9222,7 +9256,7 @@ print_backup_ref(const char *branch_name, const char *
 
 	refs = got_reflist_object_id_map_lookup(refs_idmap, new_commit_id);
 	if (refs) {
-		err = build_refs_str(&refs_str, refs, new_commit_id, repo);
+		err = build_refs_str(&refs_str, refs, new_commit_id, repo, 0);
 		if (err)
 			goto done;
 	}
@@ -9262,7 +9296,7 @@ print_backup_ref(const char *branch_name, const char *
 
 		refs = got_reflist_object_id_map_lookup(refs_idmap, yca_id);
 		if (refs) {
-			err = build_refs_str(&refs_str, refs, yca_id, repo);
+			err = build_refs_str(&refs_str, refs, yca_id, repo, 0);
 			if (err)
 				goto done;
 		}
blob - 41cee9ee65ad11031857077637457e6954320463
blob + 7bdd9c2e0c5b082a18dcf878227aa026335384cf
--- regress/cmdline/log.sh
+++ regress/cmdline/log.sh
@@ -311,14 +311,18 @@ test_log_oneline() {
 	(cd $testroot/wt && got commit -m "test oneline
 no" > /dev/null)
 	local commit_id1=`git_show_head $testroot/repo`
+	local author_time1=`git_show_author_time $testroot/repo`
 
 	echo "modified beta" > $testroot/wt/beta
 	(cd $testroot/wt && got commit -m "  test oneline
 no" > /dev/null)
 	local commit_id2=`git_show_head $testroot/repo`
+	local author_time2=`git_show_author_time $testroot/repo`
 
-	printf "%.7s test oneline\n" $commit_id2 > $testroot/stdout.expected
-	printf "%.7s test oneline\n" $commit_id1 >> $testroot/stdout.expected
+	d=`date -u -r $author_time1 +"%G-%m-%d"`
+	printf "$d %-7s test oneline\n" master > $testroot/stdout.expected
+	d=`date -u -r $author_time2 +"%G-%m-%d"`
+	printf "$d %.7s test oneline\n" $commit_id1 >> $testroot/stdout.expected
 
 	(cd $testroot/repo && got log -s | head -n 2 > $testroot/stdout)
 	cmp -s $testroot/stdout.expected $testroot/stdout