fetch: set remote/HEAD if it does not exist

When cloning a repository remote/HEAD is created, but when the user
creates a repository with git init, and later adds a remote, remote/HEAD
is only created if the user explicitly runs a variant of "remote
set-head". Attempt to set remote/HEAD during fetch, if the user does not
have it already set. Silently ignore any errors.

Signed-off-by: Bence Ferdinandy <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: ferdinandyb

builtin/fetch.c

@@ -1577,6 +1577,66 @@ static int backfill_tags(struct display_state *display_state,
 	return retcode;
 }
 
+static const char *strip_refshead(const char *name){
+	skip_prefix(name, "refs/heads/", &name);
+	return name;
+}
+
+static int set_head(const struct ref *remote_refs)
+{
+	int result = 0;
+	struct strbuf b_head = STRBUF_INIT, b_remote_head = STRBUF_INIT;
+	const char *remote = gtransport->remote->name;
+	char *head_name = NULL;
+	struct ref *ref, *matches;
+	struct ref *fetch_map = NULL, **fetch_map_tail = &fetch_map;
+	struct refspec_item refspec = {
+		.force = 0,
+		.pattern = 1,
+		.src = (char *) "refs/heads/*",
+		.dst = (char *) "refs/heads/*",
+	};
+	struct string_list heads = STRING_LIST_INIT_DUP;
+	struct ref_store *refs = get_main_ref_store(the_repository);
+
+	get_fetch_map(remote_refs, &refspec, &fetch_map_tail, 0);
+	matches = guess_remote_head(find_ref_by_name(remote_refs, "HEAD"),
+				    fetch_map, 1);
+	for (ref = matches; ref; ref = ref->next) {
+		string_list_append(&heads, strip_refshead(ref->name));
+	}
+
+
+	if (!heads.nr)
+		result = 1;
+	else if (heads.nr > 1)
+		result = 1;
+	else
+		head_name = xstrdup(heads.items[0].string);
+
+	if (!head_name)
+		goto cleanup;
+	strbuf_addf(&b_head, "refs/remotes/%s/HEAD", remote);
+	strbuf_addf(&b_remote_head, "refs/remotes/%s/%s", remote, head_name);
+		/* make sure it's valid */
+	if (!refs_ref_exists(refs, b_remote_head.buf)) {
+		result = 1;
+		goto cleanup;
+	}
+	if (refs_update_symref_extended(refs, b_head.buf, b_remote_head.buf,
+					"fetch", NULL, 1))
+		result = 1;
+
+cleanup:
+	free(head_name);
+	free_refs(fetch_map);
+	free_refs(matches);
+	string_list_clear(&heads, 0);
+	strbuf_release(&b_head);
+	strbuf_release(&b_remote_head);
+	return result;
+}
+
 static int do_fetch(struct transport *transport,
 		    struct refspec *rs,
 		    const struct fetch_config *config)
@@ -1646,6 +1706,8 @@ static int do_fetch(struct transport *transport,
 				    "refs/tags/");
 	}
 
+	strvec_push(&transport_ls_refs_options.ref_prefixes, "HEAD");
+
 	if (must_list_refs) {
 		trace2_region_enter("fetch", "remote_refs", the_repository);
 		remote_refs = transport_get_remote_refs(transport,
@@ -1790,6 +1852,12 @@ static int do_fetch(struct transport *transport,
 				  "you need to specify exactly one branch with the --set-upstream option"));
 		}
 	}
+	if (set_head(remote_refs))
+		;
+		/*
+		 * Way too many cases where this can go wrong
+		 * so let's just fail silently for now.
+		 */
 
 cleanup:
 	if (retcode) {

t/t4207-log-decoration-colors.sh

@@ -59,7 +59,8 @@ ${c_reset}${c_tag}tag: ${c_reset}${c_tag}v1.0${c_reset}${c_commit}, \
 ${c_reset}${c_tag}tag: ${c_reset}${c_tag}B${c_reset}${c_commit})${c_reset} B
 ${c_commit}COMMIT_ID${c_reset}${c_commit} (${c_reset}\
 ${c_tag}tag: ${c_reset}${c_tag}A1${c_reset}${c_commit}, \
-${c_reset}${c_remoteBranch}other/main${c_reset}${c_commit})${c_reset} A1
+${c_reset}${c_remoteBranch}other/main${c_reset}${c_commit}, \
+${c_reset}${c_remoteBranch}other/HEAD${c_reset}${c_commit})${c_reset} A1
 	${c_commit}COMMIT_ID${c_reset}${c_commit} (${c_reset}\
 ${c_stash}refs/stash${c_reset}${c_commit})${c_reset} On main: Changes to A.t
 	${c_commit}COMMIT_ID${c_reset}${c_commit} (${c_reset}\

t/t5505-remote.sh

@@ -74,7 +74,7 @@ test_expect_success 'add another remote' '
 		cd test &&
 		git remote add -f second ../two &&
 		tokens_match "origin second" "$(git remote)" &&
-		check_tracking_branch second main side another &&
+		check_tracking_branch second main side another HEAD &&
 		git for-each-ref "--format=%(refname)" refs/remotes |
 		sed -e "/^refs\/remotes\/origin\//d" \
 		    -e "/^refs\/remotes\/second\//d" >actual &&
@@ -500,7 +500,7 @@ test_expect_success 'set-head --auto has no problem w/multiple HEADs' '
 		cd test &&
 		git fetch two "refs/heads/*:refs/remotes/two/*" &&
 		git remote set-head --auto two >output 2>&1 &&
-		echo "${SQ}two/HEAD${SQ} is now created and points to ${SQ}main${SQ}" >expect &&
+		echo "${SQ}two/HEAD${SQ} is unchanged and points to ${SQ}main${SQ}" >expect &&
 		test_cmp expect output
 	)
 '
@@ -788,8 +788,10 @@ test_expect_success 'reject --no-no-tags' '
 '
 
 cat >one/expect <<\EOF
+  apis/HEAD -> apis/main
   apis/main
   apis/side
+  drosophila/HEAD -> drosophila/main
   drosophila/another
   drosophila/main
   drosophila/side
@@ -807,19 +809,22 @@ test_expect_success 'update' '
 '
 
 cat >one/expect <<\EOF
+  drosophila/HEAD -> drosophila/main
   drosophila/another
   drosophila/main
   drosophila/side
+  manduca/HEAD -> manduca/main
   manduca/main
   manduca/side
+  megaloprepus/HEAD -> megaloprepus/main
   megaloprepus/main
   megaloprepus/side
 EOF
 
 test_expect_success 'update with arguments' '
 	(
 		cd one &&
-		for b in $(git branch -r)
+		for b in $(git branch -r | grep -v HEAD)
 		do
 		git branch -r -d $b || exit 1
 		done &&
@@ -851,18 +856,21 @@ test_expect_success 'update --prune' '
 '
 
 cat >one/expect <<-\EOF
+  apis/HEAD -> apis/main
   apis/main
   apis/side
+  manduca/HEAD -> manduca/main
   manduca/main
   manduca/side
+  megaloprepus/HEAD -> megaloprepus/main
   megaloprepus/main
   megaloprepus/side
 EOF
 
 test_expect_success 'update default' '
 	(
 		cd one &&
-		for b in $(git branch -r)
+		for b in $(git branch -r | grep -v HEAD)
 		do
 		git branch -r -d $b || exit 1
 		done &&
@@ -874,6 +882,7 @@ test_expect_success 'update default' '
 '
 
 cat >one/expect <<\EOF
+  drosophila/HEAD -> drosophila/main
   drosophila/another
   drosophila/main
   drosophila/side
@@ -882,7 +891,7 @@ EOF
 test_expect_success 'update default (overridden, with funny whitespace)' '
 	(
 		cd one &&
-		for b in $(git branch -r)
+		for b in $(git branch -r | grep -v HEAD)
 		do
 		git branch -r -d $b || exit 1
 		done &&
@@ -896,7 +905,7 @@ test_expect_success 'update default (overridden, with funny whitespace)' '
 test_expect_success 'update (with remotes.default defined)' '
 	(
 		cd one &&
-		for b in $(git branch -r)
+		for b in $(git branch -r | grep -v HEAD)
 		do
 		git branch -r -d $b || exit 1
 		done &&

t/t5510-fetch.sh

@@ -75,6 +75,30 @@ test_expect_success "fetch test for-merge" '
 	cut -f -2 .git/FETCH_HEAD >actual &&
 	test_cmp expected actual'
 
+test_expect_success "fetch test remote HEAD" '
+	cd "$D" &&
+	cd two &&
+	git fetch &&
+	git rev-parse --verify refs/remotes/origin/HEAD &&
+	git rev-parse --verify refs/remotes/origin/main &&
+	head=$(git rev-parse refs/remotes/origin/HEAD) &&
+	branch=$(git rev-parse refs/remotes/origin/main) &&
+	test "z$head" = "z$branch"'
+
+test_expect_success "fetch test remote HEAD change" '
+	cd "$D" &&
+	cd two &&
+	git switch -c other &&
+	git push -u origin other &&
+	git rev-parse --verify refs/remotes/origin/HEAD &&
+	git rev-parse --verify refs/remotes/origin/main &&
+	git rev-parse --verify refs/remotes/origin/other &&
+	git remote set-head origin other &&
+	git fetch &&
+	head=$(git rev-parse refs/remotes/origin/HEAD) &&
+	branch=$(git rev-parse refs/remotes/origin/other) &&
+	test "z$head" = "z$branch"'
+
 test_expect_success 'fetch --prune on its own works as expected' '
 	cd "$D" &&
 	git clone . prune &&

t/t5512-ls-remote.sh

@@ -293,6 +293,8 @@ test_expect_success 'ls-remote with filtered symref (refname)' '
 	cat >expect <<-EOF &&
 	ref: refs/heads/main	HEAD
 	$rev	HEAD
+	ref: refs/remotes/origin/main	refs/remotes/origin/HEAD
+	$rev	refs/remotes/origin/HEAD
 	EOF
 	git ls-remote --symref . HEAD >actual &&
 	test_cmp expect actual

t/t5514-fetch-multiple.sh

@@ -45,14 +45,17 @@ test_expect_success setup '
 '
 
 cat > test/expect << EOF
+  one/HEAD -> one/main
   one/main
   one/side
   origin/HEAD -> origin/main
   origin/main
   origin/side
+  three/HEAD -> three/main
   three/another
   three/main
   three/side
+  two/HEAD -> two/main
   two/another
   two/main
   two/side
@@ -97,6 +100,7 @@ cat > expect << EOF
   origin/HEAD -> origin/main
   origin/main
   origin/side
+  three/HEAD -> three/main
   three/another
   three/main
   three/side
@@ -112,8 +116,10 @@ test_expect_success 'git fetch --multiple (but only one remote)' '
 '
 
 cat > expect << EOF
+  one/HEAD -> one/main
   one/main
   one/side
+  two/HEAD -> two/main
   two/another
   two/main
   two/side
@@ -141,7 +147,7 @@ test_expect_success 'git fetch --multiple (bad remote names)' '
 
 test_expect_success 'git fetch --all (skipFetchAll)' '
 	(cd test4 &&
-	 for b in $(git branch -r)
+	 for b in $(git branch -r | grep -v HEAD)
 	 do
 		git branch -r -d $b || exit 1
 	 done &&
@@ -153,19 +159,22 @@ test_expect_success 'git fetch --all (skipFetchAll)' '
 '
 
 cat > expect << EOF
+  one/HEAD -> one/main
   one/main
   one/side
+  three/HEAD -> three/main
   three/another
   three/main
   three/side
+  two/HEAD -> two/main
   two/another
   two/main
   two/side
 EOF
 
 test_expect_success 'git fetch --multiple (ignoring skipFetchAll)' '
 	(cd test4 &&
-	 for b in $(git branch -r)
+	 for b in $(git branch -r | grep -v HEAD)
 	 do
 		git branch -r -d $b || exit 1
 	 done &&
@@ -221,14 +230,17 @@ test_expect_success 'git fetch --multiple --jobs=0 picks a default' '
 
 create_fetch_all_expect () {
 	cat >expect <<-\EOF
+	  one/HEAD -> one/main
 	  one/main
 	  one/side
 	  origin/HEAD -> origin/main
 	  origin/main
 	  origin/side
+	  three/HEAD -> three/main
 	  three/another
 	  three/main
 	  three/side
+	  two/HEAD -> two/main
 	  two/another
 	  two/main
 	  two/side
@@ -265,6 +277,7 @@ test_expect_success 'git fetch (fetch all remotes with fetch.all = true)' '
 
 create_fetch_one_expect () {
 	cat >expect <<-\EOF
+	  one/HEAD -> one/main
 	  one/main
 	  one/side
 	  origin/HEAD -> origin/main

t/t5516-fetch-push.sh

@@ -1395,7 +1395,8 @@ test_expect_success 'fetch follows tags by default' '
 		git tag -m "annotated" tag &&
 		git for-each-ref >tmp1 &&
 		sed -n "p; s|refs/heads/main$|refs/remotes/origin/main|p" tmp1 |
-		sort -k 3 >../expect
+		sed -n "p; s|refs/heads/main$|refs/remotes/origin/HEAD|p"  |
+		sort -k 4 >../expect
 	) &&
 	test_when_finished "rm -rf dst" &&
 	git init dst &&

t/t5527-fetch-odd-refs.sh

@@ -52,7 +52,8 @@ test_expect_success LONG_REF 'fetch handles extremely long refname' '
 	long
 	main
 	EOF
-	git for-each-ref --format="%(subject)" refs/remotes/long >actual &&
+	git for-each-ref --format="%(subject)" refs/remotes/long \
+		--exclude=refs/remotes/long/HEAD >actual &&
 	test_cmp expect actual
 '
 

t/t7900-maintenance.sh

@@ -328,7 +328,8 @@ test_expect_success 'incremental-repack task' '
 
 	# Delete refs that have not been repacked in these packs.
 	git for-each-ref --format="delete %(refname)" \
-		refs/prefetch refs/tags refs/remotes >refs &&
+		refs/prefetch refs/tags refs/remotes \
+		--exclude=refs/remotes/*/HEAD >refs &&
 	git update-ref --stdin <refs &&
 
 	# Replace the object directory with this pack layout.

t/t9210-scalar.sh

@@ -150,7 +150,8 @@ test_expect_success 'scalar clone' '
 			"$(pwd)" &&
 
 		git for-each-ref --format="%(refname)" refs/remotes/origin/ >actual &&
-		echo "refs/remotes/origin/parallel" >expect &&
+		echo "refs/remotes/origin/HEAD" >>expect &&
+		echo "refs/remotes/origin/parallel" >>expect &&
 		test_cmp expect actual &&
 
 		test_path_is_missing 1/2 &&
@@ -219,7 +220,7 @@ test_expect_success 'scalar reconfigure --all with includeIf.onbranch' '
 	done
 '
 
- test_expect_success 'scalar reconfigure --all with detached HEADs' '
+test_expect_success 'scalar reconfigure --all with detached HEADs' '
 	repos="two three four" &&
 	for num in $repos
 	do