[PATCH v4] remote: add --save-to-push option to git remote set-url

[Denton Liu <liu.denton@gmail.com>]

This adds the --save-to-push option to `git remote set-url` such that
when executed, we move the remote.*.url to remote.*.pushurl and set
remote.*.url to the given url argument.

For example, if we have the following config:

	[remote "origin"]
		url = git@github.com:git/git.git

`git remote set-url --save-to-push origin https://github.com/git/git.git`
would change the config to the following:

	[remote "origin"]
		url = https://github.com/git/git.git
		pushurl = git@github.com:git/git.git

Helped-by: Junio C Hamano <gitster@pobox.com>
Signed-off-by: Denton Liu <liu.denton@gmail.com>
---

This patch improves upon v3 by adding the use-case for the new option,
as discussed here[1].

[1]: https://public-inbox.org/git/xmqqtvjlisnu.fsf@gitster-ct.c.googlers.com/
---
 Documentation/git-remote.txt | 12 ++++++++++++
 builtin/remote.c             | 26 +++++++++++++++++++++-----
 t/t5505-remote.sh            | 11 +++++++++++
 3 files changed, 44 insertions(+), 5 deletions(-)

diff --git a/Documentation/git-remote.txt b/Documentation/git-remote.txt
index 0cad37fb81..47aaae22c1 100644
--- a/Documentation/git-remote.txt
+++ b/Documentation/git-remote.txt
@@ -19,6 +19,7 @@ SYNOPSIS
 'git remote set-url' [--push] <name> <newurl> [<oldurl>]
 'git remote set-url --add' [--push] <name> <newurl>
 'git remote set-url --delete' [--push] <name> <url>
+'git remote set-url --save-to-push' <name> <url>
 'git remote' [-v | --verbose] 'show' [-n] <name>...
 'git remote prune' [-n | --dry-run] <name>...
 'git remote' [-v | --verbose] 'update' [-p | --prune] [(<group> | <remote>)...]
@@ -155,6 +156,17 @@ With `--delete`, instead of changing existing URLs, all URLs matching
 regex <url> are deleted for remote <name>.  Trying to delete all
 non-push URLs is an error.
 +
+With `--save-to-push`, the current URL is saved into the push URL before
+setting the URL to <url>. Note that this command will not work if more than one
+URL is defined because the behavior would be ambiguous. A use-case for this
+feature is that you may have started your interaction with the repository with
+a single authenticated URL that can be used for both fetching and pushing, but
+over time you may have become sick of having to authenticate only to fetch.  In
+such a case, you can feed an unauthenticated/anonymous fetch URL to set-url
+with this option, so that the authenticated URL that you have been using for
+pushing becomes the pushURL, and the new, unauthenticated/anonymous URL will be
+used for fetching.
++
 Note that the push URL and the fetch URL, even though they can
 be set differently, must still refer to the same place.  What you
 pushed to the push URL should be what you would see if you
diff --git a/builtin/remote.c b/builtin/remote.c
index f7edf7f2cb..d683e67ba6 100644
--- a/builtin/remote.c
+++ b/builtin/remote.c
@@ -24,8 +24,9 @@ static const char * const builtin_remote_usage[] = {
 	N_("git remote set-branches [--add] <name> <branch>..."),
 	N_("git remote get-url [--push] [--all] <name>"),
 	N_("git remote set-url [--push] <name> <newurl> [<oldurl>]"),
-	N_("git remote set-url --add <name> <newurl>"),
-	N_("git remote set-url --delete <name> <url>"),
+	N_("git remote set-url --add [--push] <name> <newurl>"),
+	N_("git remote set-url --delete [--push] <name> <url>"),
+	N_("git remote set-url --save-to-push <name> <url>"),
 	NULL
 };
 
@@ -77,8 +78,9 @@ static const char * const builtin_remote_geturl_usage[] = {
 
 static const char * const builtin_remote_seturl_usage[] = {
 	N_("git remote set-url [--push] <name> <newurl> [<oldurl>]"),
-	N_("git remote set-url --add <name> <newurl>"),
-	N_("git remote set-url --delete <name> <url>"),
+	N_("git remote set-url --add [--push] <name> <newurl>"),
+	N_("git remote set-url --delete [--push] <name> <url>"),
+	N_("git remote set-url --save-to-push <name> <url>"),
 	NULL
 };
 
@@ -1519,7 +1521,7 @@ static int get_url(int argc, const char **argv)
 
 static int set_url(int argc, const char **argv)
 {
-	int i, push_mode = 0, add_mode = 0, delete_mode = 0;
+	int i, push_mode = 0, save_to_push = 0, add_mode = 0, delete_mode = 0;
 	int matches = 0, negative_matches = 0;
 	const char *remotename = NULL;
 	const char *newurl = NULL;
@@ -1532,6 +1534,8 @@ static int set_url(int argc, const char **argv)
 	struct option options[] = {
 		OPT_BOOL('\0', "push", &push_mode,
 			 N_("manipulate push URLs")),
+		OPT_BOOL('\0', "save-to-push", &save_to_push,
+			 N_("change fetching URL behavior")),
 		OPT_BOOL('\0', "add", &add_mode,
 			 N_("add URL")),
 		OPT_BOOL('\0', "delete", &delete_mode,
@@ -1543,6 +1547,8 @@ static int set_url(int argc, const char **argv)
 
 	if (add_mode && delete_mode)
 		die(_("--add --delete doesn't make sense"));
+	if (save_to_push && (push_mode || add_mode || delete_mode))
+		die(_("--save-to-push cannot be used with other options"));
 
 	if (argc < 3 || argc > 4 || ((add_mode || delete_mode) && argc != 3))
 		usage_with_options(builtin_remote_seturl_usage, options);
@@ -1564,6 +1570,16 @@ static int set_url(int argc, const char **argv)
 		urlset = remote->pushurl;
 		urlset_nr = remote->pushurl_nr;
 	} else {
+		if (save_to_push) {
+			if (remote->url_nr != 1)
+				die(_("--save-to-push can only be used when only one url is defined"));
+
+			strbuf_addf(&name_buf, "remote.%s.pushurl", remotename);
+			git_config_set_multivar(name_buf.buf,
+			      remote->url[0], "^$", 0);
+			strbuf_reset(&name_buf);
+		}
+
 		strbuf_addf(&name_buf, "remote.%s.url", remotename);
 		urlset = remote->url;
 		urlset_nr = remote->url_nr;
diff --git a/t/t5505-remote.sh b/t/t5505-remote.sh
index d2a2cdd453..434c1f828a 100755
--- a/t/t5505-remote.sh
+++ b/t/t5505-remote.sh
@@ -1194,6 +1194,17 @@ test_expect_success 'remote set-url --delete baz' '
 	cmp expect actual
 '
 
+test_expect_success 'remote set-url --save-to-push bbb' '
+	git remote set-url --save-to-push someremote bbb &&
+	echo bbb >expect &&
+	echo "YYY" >>expect &&
+	echo ccc >>expect &&
+	git config --get-all remote.someremote.url >actual &&
+	echo "YYY" >>actual &&
+	git config --get-all remote.someremote.pushurl >>actual &&
+	cmp expect actual
+'
+
 test_expect_success 'extra args: setup' '
 	# add a dummy origin so that this does not trigger failure
 	git remote add origin .
-- 
2.19.2