push: add an advice on unqualified <dst> push

Add an advice to the recently improved error message added in
f8aae12034 ("push: allow unqualified dest refspecs to DWIM",
2008-04-23).

Now with advice.pushUnqualifiedRefName=true (on by default) we show a
hint about how to proceed:

    $ ./git-push avar v2.19.0^{commit}:newbranch -n
    error: The destination you provided is not a full refname (i.e.,
    starting with "refs/"). We tried to guess what you meant by:

    - Looking for a ref that matches 'newbranch' on the remote side.
    - Checking if the <src> being pushed ('v2.19.0^{commit}')
      is a ref in "refs/{heads,tags}/". If so we add a corresponding
      refs/{heads,tags}/ prefix on the remote side.

    Neither worked, so we gave up. You must fully qualify the ref.
    hint: The <src> part of the refspec is a commit object.
    hint: Did you mean to create a new branch by pushing to
    hint: 'v2.19.0^{commit}:refs/heads/newbranch'?
    error: failed to push some refs to 'git@github.com:avar/git.git'

When trying to push a tag, tree or a blob we suggest that perhaps the
user meant to push them to refs/tags/ instead.

The if/else duplication for all of OBJ_{COMMIT,TAG,TREE,BLOB} is
unfortunate, but is required to correctly mark the messages for
translation. See the discussion in
<87r2gxebsi.fsf@evledraar.gmail.com> about that.

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

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

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 };
 
@@ -1008,6 +1009,9 @@ 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
@@ -1023,6 +1027,39 @@ static void show_push_unqualified_ref_name_error(const char *dst_value,
 		"\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,

t/t5505-remote.sh

@@ -1222,4 +1222,32 @@ 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_done