Merge branch 'ab/push-dwim-dst'

"git push $there $src:$dst" rejects when $dst is not a fully
qualified refname and not clear what the end user meant.  The
codepath has been taught to give a clearer error message, and also
guess where the push should go by taking the type of the pushed
object into account (e.g. a tag object would want to go under
refs/tags/).

* ab/push-dwim-dst:
  push doc: document the DWYM behavior pushing to unqualified <dst>
  push: test that <src> doesn't DWYM if <dst> is unqualified
  push: add an advice on unqualified <dst> push
  push: move unqualified refname error into a function
  push: improve the error shown on unqualified <dst> push
  i18n: remote.c: mark error(...) messages for translation
  remote.c: add braces in anticipation of a follow-up change

Documentation/config/advice.txt

@@ -30,6 +30,13 @@ advice.*::
 		tries to overwrite a remote ref that points at an
 		object that is not a commit-ish, or make the remote
 		ref point at an object that is not a commit-ish.
+	pushUnqualifiedRefname::
+		Shown when linkgit:git-push[1] gives up trying to
+		guess based on the source and destination refs what
+		remote ref namespace the source belongs in, but where
+		we can still suggest that the user push to either
+		refs/heads/* or refs/tags/* based on the type of the
+		source object.
 	statusHints::
 		Show directions on how to proceed from the current
 		state in the output of linkgit:git-status[1], in

Documentation/git-push.txt

@@ -73,6 +73,26 @@ be omitted--such a push will update a ref that `<src>` normally updates
 without any `<refspec>` on the command line.  Otherwise, missing
 `:<dst>` means to update the same ref as the `<src>`.
 +
+If <dst> doesn't start with `refs/` (e.g. `refs/heads/master`) we will
+try to infer where in `refs/*` on the destination <repository> it
+belongs based on the the type of <src> being pushed and whether <dst>
+is ambiguous.
++
+--
+* If <dst> unambiguously refers to a ref on the <repository> remote,
+  then push to that ref.
+
+* If <src> resolves to a ref starting with refs/heads/ or refs/tags/,
+  then prepend that to <dst>.
+
+* Other ambiguity resolutions might be added in the future, but for
+  now any other cases will error out with an error indicating what we
+  tried, and depending on the `advice.pushUnqualifiedRefname`
+  configuration (see linkgit:git-config[1]) suggest what refs/
+  namespace you may have wanted to push to.
+
+--
++
 The object referenced by <src> is used to update the <dst> reference
 on the remote side. Whether this is allowed depends on where in
 `refs/*` the <dst> reference lives as described in detail below, in
@@ -591,6 +611,9 @@ the ones in the examples below) can be configured as the default for
 	`refs/remotes/satellite/master`) in the `mothership` repository;
 	do the same for `dev` and `satellite/dev`.
 +
+See the section describing `<refspec>...` above for a discussion of
+the matching semantics.
++
 This is to emulate `git fetch` run on the `mothership` using `git
 push` that is run in the opposite direction in order to integrate
 the work done on `satellite`, and is often necessary when you can

advice.c

@@ -9,6 +9,7 @@ int advice_push_non_ff_matching = 1;
 int advice_push_already_exists = 1;
 int advice_push_fetch_first = 1;
 int advice_push_needs_force = 1;
+int advice_push_unqualified_ref_name = 1;
 int advice_status_hints = 1;
 int advice_status_u_option = 1;
 int advice_commit_before_merge = 1;
@@ -63,6 +64,7 @@ static struct {
 	{ "pushAlreadyExists", &advice_push_already_exists },
 	{ "pushFetchFirst", &advice_push_fetch_first },
 	{ "pushNeedsForce", &advice_push_needs_force },
+	{ "pushUnqualifiedRefName", &advice_push_unqualified_ref_name },
 	{ "statusHints", &advice_status_hints },
 	{ "statusUoption", &advice_status_u_option },
 	{ "commitBeforeMerge", &advice_commit_before_merge },

advice.h

@@ -9,6 +9,7 @@ extern int advice_push_non_ff_matching;
 extern int advice_push_already_exists;
 extern int advice_push_fetch_first;
 extern int advice_push_needs_force;
+extern int advice_push_unqualified_ref_name;
 extern int advice_status_hints;
 extern int advice_status_u_option;
 extern int advice_commit_before_merge;

remote.c

@@ -13,6 +13,7 @@
 #include "mergesort.h"
 #include "argv-array.h"
 #include "commit-reach.h"
+#include "advice.h"
 
 enum map_direction { FROM_SRC, FROM_DST };
 
@@ -968,12 +969,13 @@ static char *guess_ref(const char *name, struct ref *peer)
 	if (!r)
 		return NULL;
 
-	if (starts_with(r, "refs/heads/"))
+	if (starts_with(r, "refs/heads/")) {
 		strbuf_addstr(&buf, "refs/heads/");
-	else if (starts_with(r, "refs/tags/"))
+	} else if (starts_with(r, "refs/tags/")) {
 		strbuf_addstr(&buf, "refs/tags/");
-	else
+	} else {
 		return NULL;
+	}
 
 	strbuf_addstr(&buf, name);
 	return strbuf_detach(&buf, NULL);
@@ -1004,6 +1006,62 @@ static int match_explicit_lhs(struct ref *src,
 	}
 }
 
+static void show_push_unqualified_ref_name_error(const char *dst_value,
+						 const char *matched_src_name)
+{
+	struct object_id oid;
+	enum object_type type;
+
+	/*
+	 * TRANSLATORS: "matches '%s'%" is the <dst> part of "git push
+	 * <remote> <src>:<dst>" push, and "being pushed ('%s')" is
+	 * the <src>.
+	 */
+	error(_("The destination you provided is not a full refname (i.e.,\n"
+		"starting with \"refs/\"). We tried to guess what you meant by:\n"
+		"\n"
+		"- Looking for a ref that matches '%s' on the remote side.\n"
+		"- Checking if the <src> being pushed ('%s')\n"
+		"  is a ref in \"refs/{heads,tags}/\". If so we add a corresponding\n"
+		"  refs/{heads,tags}/ prefix on the remote side.\n"
+		"\n"
+		"Neither worked, so we gave up. You must fully qualify the ref."),
+	      dst_value, matched_src_name);
+
+	if (!advice_push_unqualified_ref_name)
+		return;
+
+	if (get_oid(matched_src_name, &oid))
+		BUG("'%s' is not a valid object, "
+		    "match_explicit_lhs() should catch this!",
+		    matched_src_name);
+	type = oid_object_info(the_repository, &oid, NULL);
+	if (type == OBJ_COMMIT) {
+		advise(_("The <src> part of the refspec is a commit object.\n"
+			 "Did you mean to create a new branch by pushing to\n"
+			 "'%s:refs/heads/%s'?"),
+		       matched_src_name, dst_value);
+	} else if (type == OBJ_TAG) {
+		advise(_("The <src> part of the refspec is a tag object.\n"
+			 "Did you mean to create a new tag by pushing to\n"
+			 "'%s:refs/tags/%s'?"),
+		       matched_src_name, dst_value);
+	} else if (type == OBJ_TREE) {
+		advise(_("The <src> part of the refspec is a tree object.\n"
+			 "Did you mean to tag a new tree by pushing to\n"
+			 "'%s:refs/tags/%s'?"),
+		       matched_src_name, dst_value);
+	} else if (type == OBJ_BLOB) {
+		advise(_("The <src> part of the refspec is a blob object.\n"
+			 "Did you mean to tag a new blob by pushing to\n"
+			 "'%s:refs/tags/%s'?"),
+		       matched_src_name, dst_value);
+	} else {
+		BUG("'%s' should be commit/tag/tree/blob, is '%d'",
+		    matched_src_name, type);
+	}
+}
+
 static int match_explicit(struct ref *src, struct ref *dst,
 			  struct ref ***dst_tail,
 			  struct refspec_item *rs)
@@ -1038,21 +1096,18 @@ static int match_explicit(struct ref *src, struct ref *dst,
 	case 1:
 		break;
 	case 0:
-		if (starts_with(dst_value, "refs/"))
+		if (starts_with(dst_value, "refs/")) {
 			matched_dst = make_linked_ref(dst_value, dst_tail);
-		else if (is_null_oid(&matched_src->new_oid))
+		} else if (is_null_oid(&matched_src->new_oid)) {
 			error(_("unable to delete '%s': remote ref does not exist"),
 			      dst_value);
-		else if ((dst_guess = guess_ref(dst_value, matched_src))) {
+		} else if ((dst_guess = guess_ref(dst_value, matched_src))) {
 			matched_dst = make_linked_ref(dst_guess, dst_tail);
 			free(dst_guess);
-		} else
-			error(_("unable to push to unqualified destination: %s\n"
-				"The destination refspec neither matches an "
-				"existing ref on the remote nor\n"
-				"begins with refs/, and we are unable to "
-				"guess a prefix based on the source ref."),
-			      dst_value);
+		} else {
+			show_push_unqualified_ref_name_error(dst_value,
+							     matched_src->name);
+		}
 		break;
 	default:
 		matched_dst = NULL;

t/t5505-remote.sh

@@ -1222,4 +1222,59 @@ test_expect_success 'add remote matching the "insteadOf" URL' '
 	git remote add backup xyz@example.com
 '
 
+test_expect_success 'unqualified <dst> refspec DWIM and advice' '
+	test_when_finished "(cd test && git tag -d some-tag)" &&
+	(
+		cd test &&
+		git tag -a -m "Some tag" some-tag master &&
+		exit_with=true &&
+		for type in commit tag tree blob
+		do
+			if test "$type" = "blob"
+			then
+				oid=$(git rev-parse some-tag:file)
+			else
+				oid=$(git rev-parse some-tag^{$type})
+			fi &&
+			test_must_fail git push origin $oid:dst 2>err &&
+			test_i18ngrep "error: The destination you" err &&
+			test_i18ngrep "hint: Did you mean" err &&
+			test_must_fail git -c advice.pushUnqualifiedRefName=false \
+				push origin $oid:dst 2>err &&
+			test_i18ngrep "error: The destination you" err &&
+			test_i18ngrep ! "hint: Did you mean" err ||
+			exit_with=false
+		done &&
+		$exit_with
+	)
+'
+
+test_expect_success 'refs/remotes/* <src> refspec and unqualified <dst> DWIM and advice' '
+	(
+		cd two &&
+		git tag -a -m "Some tag" my-tag master &&
+		git update-ref refs/trees/my-head-tree HEAD^{tree} &&
+		git update-ref refs/blobs/my-file-blob HEAD:file
+	) &&
+	(
+		cd test &&
+		git config --add remote.two.fetch "+refs/tags/*:refs/remotes/tags-from-two/*" &&
+		git config --add remote.two.fetch "+refs/trees/*:refs/remotes/trees-from-two/*" &&
+		git config --add remote.two.fetch "+refs/blobs/*:refs/remotes/blobs-from-two/*" &&
+		git fetch --no-tags two &&
+
+		test_must_fail git push origin refs/remotes/two/another:dst 2>err &&
+		test_i18ngrep "error: The destination you" err &&
+
+		test_must_fail git push origin refs/remotes/tags-from-two/my-tag:dst-tag 2>err &&
+		test_i18ngrep "error: The destination you" err &&
+
+		test_must_fail git push origin refs/remotes/trees-from-two/my-head-tree:dst-tree 2>err &&
+		test_i18ngrep "error: The destination you" err &&
+
+		test_must_fail git push origin refs/remotes/blobs-from-two/my-file-blob:dst-blob 2>err &&
+		test_i18ngrep "error: The destination you" err
+	)
+'
+
 test_done