[PATCH] pull, fetch: add --set-upstream option

[Matthieu Moy <git@matthieu-moy.fr>]

From: Corentin BOMPARD <corentin.bompard@etu.univ-lyon1.fr>

Add the --set-upstream option to git pull/fetch
which lets the user set the upstream configuration
(branch.<current-branch-name>.merge and
branch.<current-branch-name>.remote) for the current branch.

A typical use-case is:

    git clone http://example.com/my-public-fork
    git remote add main http://example.com/project-main-repo
    git pull --set-upstream main master

or, instead of the last line:

    git fetch --set-upstream main master
    git merge # or git rebase

This functionality is analog to push --set-upstream.

Signed-off-by: Corentin BOMPARD <corentin.bompard@etu.univ-lyon1.fr>
Signed-off-by: Nathan BERBEZIER <nathan.berbezier@etu.univ-lyon1.fr>
Signed-off-by: Pablo CHABANNE <pablo.chabanne@etu.univ-lyon1.fr>
Signed-off-by: Matthieu Moy <git@matthieu-moy.fr>
Patch-edited-by: Matthieu Moy <git@matthieu-moy.fr>
---
This is a followup on
https://public-inbox.org/git/86zhoil3yw.fsf@univ-lyon1.fr/. It's
initially a student project, but students didn't get time to complete
it. Still, I think the feature is interesting, and I finally get time
to fix the remarks made up to now. This now looks good to me, but
obviously needs other pairs of eyes.

Thanks,

 Documentation/fetch-options.txt |   7 ++
 builtin/fetch.c                 |  48 ++++++++-
 builtin/pull.c                  |   6 ++
 t/t5553-set-upstream.sh         | 178 ++++++++++++++++++++++++++++++++
 4 files changed, 238 insertions(+), 1 deletion(-)
 create mode 100755 t/t5553-set-upstream.sh

diff --git a/Documentation/fetch-options.txt b/Documentation/fetch-options.txt
index 3c9b4f9e09..99df1f3d4e 100644
--- a/Documentation/fetch-options.txt
+++ b/Documentation/fetch-options.txt
@@ -169,6 +169,13 @@ ifndef::git-pull[]
 	Disable recursive fetching of submodules (this has the same effect as
 	using the `--recurse-submodules=no` option).
 
+--set-upstream::
+	If the remote is fetched successfully, pull and add upstream
+	(tracking) reference, used by argument-less
+	linkgit:git-pull[1] and other commands. For more information,
+	see `branch.<name>.merge` and `branch.<name>.remote` in
+	linkgit:git-config[1].
+
 --submodule-prefix=<path>::
 	Prepend <path> to paths printed in informative messages
 	such as "Fetching submodule foo".  This option is used
diff --git a/builtin/fetch.c b/builtin/fetch.c
index 717dd14e89..5557ae1c04 100644
--- a/builtin/fetch.c
+++ b/builtin/fetch.c
@@ -23,6 +23,7 @@
 #include "packfile.h"
 #include "list-objects-filter-options.h"
 #include "commit-reach.h"
+#include "branch.h"
 
 #define FORCED_UPDATES_DELAY_WARNING_IN_MS (10 * 1000)
 
@@ -50,7 +51,7 @@ static int fetch_prune_tags_config = -1; /* unspecified */
 static int prune_tags = -1; /* unspecified */
 #define PRUNE_TAGS_BY_DEFAULT 0 /* do we prune tags by default? */
 
-static int all, append, dry_run, force, keep, multiple, update_head_ok, verbosity, deepen_relative;
+static int all, append, dry_run, force, keep, multiple, update_head_ok, verbosity, deepen_relative, set_upstream;
 static int progress = -1;
 static int enable_auto_gc = 1;
 static int tags = TAGS_DEFAULT, unshallow, update_shallow, deepen;
@@ -123,6 +124,8 @@ static struct option builtin_fetch_options[] = {
 	OPT__VERBOSITY(&verbosity),
 	OPT_BOOL(0, "all", &all,
 		 N_("fetch from all remotes")),
+	OPT_BOOL(0, "set-upstream", &set_upstream,
+		 N_("set upstream for git pull/fetch")),
 	OPT_BOOL('a', "append", &append,
 		 N_("append to .git/FETCH_HEAD instead of overwriting")),
 	OPT_STRING(0, "upload-pack", &upload_pack, N_("path"),
@@ -1367,6 +1370,49 @@ static int do_fetch(struct transport *transport,
 		retcode = 1;
 		goto cleanup;
 	}
+
+	if (set_upstream) {
+		struct branch *branch = branch_get("HEAD");
+		struct ref *rm;
+		struct ref *source_ref = NULL;
+
+		/*
+		 * We're setting the upstream configuration for the current branch. The
+		 * relevent upstream is the fetched branch that is meant to be merged with
+		 * the current one, i.e. the one fetched to FETCH_HEAD.
+		 *
+		 * When there are several such branches, consider the request ambiguous and
+		 * err on the safe side by doing nothing and just emit a warning.
+		 */
+		for (rm = ref_map; rm; rm = rm->next) {
+			if (!rm->peer_ref) {
+				if (source_ref) {
+					warning(_("multiple branch detected, incompatible with --set-upstream"));
+					goto skip;
+				} else {
+					source_ref = rm;
+				}
+			}
+		}
+		if (source_ref) {
+			if (!strcmp(source_ref->name, "HEAD") || 
+				starts_with(source_ref->name, "refs/heads/")) {
+				install_branch_config(0, branch->name,
+							 transport->remote->name,
+							 source_ref->name);
+			} else if (starts_with(source_ref->name, "refs/remotes/")) {
+				warning(_("not setting upstream for a remote remote-tracking branch"));
+			} else if (starts_with(source_ref->name, "refs/tags/")) {
+				warning(_("not setting upstream for a remote tag"));
+			} else {
+				warning(_("unknown branch type"));
+			}
+		} else {
+			warning(_("no source branch found.\n"
+				"you need to specify exactly one branch with the --set-upstream option."));
+		}
+	}
+ skip:
 	free_refs(ref_map);
 
 	/* if neither --no-tags nor --tags was specified, do automated tag
diff --git a/builtin/pull.c b/builtin/pull.c
index f1eaf6e6ed..d25ff13a60 100644
--- a/builtin/pull.c
+++ b/builtin/pull.c
@@ -129,6 +129,7 @@ static char *opt_refmap;
 static char *opt_ipv4;
 static char *opt_ipv6;
 static int opt_show_forced_updates = -1;
+static char *set_upstream;
 
 static struct option pull_options[] = {
 	/* Shared options */
@@ -243,6 +244,9 @@ static struct option pull_options[] = {
 		PARSE_OPT_NOARG),
 	OPT_BOOL(0, "show-forced-updates", &opt_show_forced_updates,
 		 N_("check for forced-updates on all updated branches")),
+	OPT_PASSTHRU(0, "set-upstream", &set_upstream, NULL,
+		N_("set upstream for git pull/fetch"),
+		PARSE_OPT_NOARG),
 
 	OPT_END()
 };
@@ -556,6 +560,8 @@ static int run_fetch(const char *repo, const char **refspecs)
 		argv_array_push(&args, "--show-forced-updates");
 	else if (opt_show_forced_updates == 0)
 		argv_array_push(&args, "--no-show-forced-updates");
+	if (set_upstream)
+		argv_array_push(&args, set_upstream);
 
 	if (repo) {
 		argv_array_push(&args, repo);
diff --git a/t/t5553-set-upstream.sh b/t/t5553-set-upstream.sh
new file mode 100755
index 0000000000..bd1a94f494
--- /dev/null
+++ b/t/t5553-set-upstream.sh
@@ -0,0 +1,178 @@
+#!/bin/sh
+
+test_description='"git fetch/pull --set-upstream" basic tests.'
+. ./test-lib.sh
+
+check_config () {
+	printf "%s\n" "$2" "$3" >"expect.$1" &&
+	{
+		git config "branch.$1.remote" && git config "branch.$1.merge"
+	} >"actual.$1" &&
+	test_cmp "expect.$1" "actual.$1"
+}
+
+check_config_missing () {
+	test_expect_code 1 git config "branch.$1.remote" &&
+	test_expect_code 1 git config "branch.$1.merge"
+}
+
+clear_config () {
+	for branch in "$@"; do
+		test_might_fail git config --unset-all "branch.$branch.remote"
+		test_might_fail git config --unset-all "branch.$branch.merge"
+	done
+}
+
+ensure_fresh_upstream () {
+	rm -rf parent && git init --bare parent
+}
+
+test_expect_success 'setup bare parent fetch' '
+	ensure_fresh_upstream &&
+	git remote add upstream parent
+'
+
+test_expect_success 'setup commit on master and other fetch' '
+	test_commit one &&
+	git push upstream master &&
+	git checkout -b other &&
+	test_commit two &&
+	git push upstream other
+'
+
+#tests for fetch --set-upstream
+
+test_expect_success 'fetch --set-upstream does not set upstream w/o branch' '
+	clear_config master other &&
+	git checkout master &&
+	git fetch --set-upstream upstream &&
+	check_config_missing master &&
+	check_config_missing other
+'
+
+test_expect_success 'fetch --set-upstream upstream master sets branch master but not other' '
+	clear_config master other &&
+	git fetch --set-upstream upstream master &&
+	check_config master upstream refs/heads/master &&
+	check_config_missing other
+'
+
+test_expect_success 'fetch --set-upstream upstream other sets branch other' '
+	clear_config master other &&
+	git fetch --set-upstream upstream other &&
+	check_config master upstream refs/heads/other &&
+	check_config_missing other
+'
+
+test_expect_success 'fetch --set-upstream master:other does not set the branch other2' '
+	clear_config other2 &&
+	git fetch --set-upstream upstream master:other2 &&
+	check_config_missing other2
+'
+
+test_expect_success 'fetch --set-upstream http://nosuchdomain.example.com fails with invalid url' '
+	# master explicitly not cleared, we check that it is not touched from previous value
+	clear_config other other2 &&
+	test_must_fail git fetch --set-upstream http://nosuchdomain.example.com &&
+	check_config master upstream refs/heads/other &&
+	check_config_missing other &&
+	check_config_missing other2
+'
+
+test_expect_success 'fetch --set-upstream with valid URL sets upstream to URL' '
+	clear_config other other2 &&
+	url="file://'"$PWD"'" &&
+	git fetch --set-upstream "$url" &&
+	check_config master "$url" HEAD &&
+	check_config_missing other &&
+	check_config_missing other2
+'
+
+#tests for pull --set-upstream
+
+test_expect_success 'setup bare parent pull' '
+	git remote rm upstream &&
+	ensure_fresh_upstream &&
+	git remote add upstream parent
+'
+
+test_expect_success 'setup commit on master and other pull' '
+	test_commit three &&
+	git push --tags upstream master &&
+	test_commit four &&
+	git push upstream other
+'
+
+test_expect_success 'pull --set-upstream upstream master sets branch master but not other' '
+	clear_config master other &&
+	git pull --set-upstream upstream master &&
+	check_config master upstream refs/heads/master &&
+	check_config_missing other
+'
+
+test_expect_success 'pull --set-upstream master:other2 does not set the branch other2' '
+	clear_config other2 &&
+	git pull --set-upstream upstream master:other2 &&
+	check_config_missing other2
+'
+
+test_expect_success 'pull --set-upstream upstream other sets branch master' '
+	clear_config master other &&
+	git pull --set-upstream upstream other &&
+	check_config master upstream refs/heads/other &&
+	check_config_missing other
+'
+
+test_expect_success 'pull --set-upstream upstream tag does not set the tag' '
+	clear_config three &&
+	git pull --tags --set-upstream upstream three &&
+	check_config_missing three
+'
+
+test_expect_success 'pull --set-upstream http://nosuchdomain.example.com fails with invalid url' '
+	# master explicitly not cleared, we check that it is not touched from previous value
+	clear_config other other2 three &&
+	test_must_fail git pull --set-upstream http://nosuchdomain.example.com &&
+	check_config master upstream refs/heads/other &&
+	check_config_missing other &&
+	check_config_missing other2 &&
+	check_config_missing three
+'
+
+test_expect_success 'pull --set-upstream upstream HEAD sets branch HEAD' '
+	clear_config master other &&
+	git pull --set-upstream upstream HEAD &&
+	check_config master upstream HEAD &&
+	git checkout other &&
+	git pull --set-upstream upstream HEAD &&
+	check_config other upstream HEAD
+'
+
+test_expect_success 'pull --set-upstream upstream with more than one branch does nothing' '
+	clear_config master three &&
+	git pull --set-upstream upstream master three &&
+	check_config_missing master &&
+	check_config_missing three
+'
+
+test_expect_success 'pull --set-upstream with valid URL sets upstream to URL' '
+	clear_config master other other2 &&
+	git checkout master &&
+	url="file://'"$PWD"'" &&
+	git pull --set-upstream "$url" &&
+	check_config master "$url" HEAD &&
+	check_config_missing other &&
+	check_config_missing other2
+'
+
+test_expect_success 'pull --set-upstream with valid URL and branch sets branch' '
+	clear_config master other other2 &&
+	git checkout master &&
+	url="file://'"$PWD"'" &&
+	git pull --set-upstream "$url" master &&
+	check_config master "$url" refs/heads/master &&
+	check_config_missing other &&
+	check_config_missing other2
+'
+
+test_done
-- 
2.20.1.98.gecbdaf0