[PATCH 2/3] for-each-ref: let upstream/push optionally report merge name.

[Johannes Schindelin <johannes.schindelin@gmx.de>]

From: J Wyman <jwyman@microsoft.com>

There are times when scripts want to know not only the name of the
push branch on the remote, but also the name of the branch as known
by the remote repository.

A useful example of this is with the push command where
`branch.<name>.merge` is useful as the <to> value. Example:

	$ git push <remote> <from>:<to>

This patch offers the new suffix :merge for the push atom, allowing to
show exactly that. Example:

	$ cat .git/config
	...
	[remote "origin"]
		url = https://where.do.we.come/from
		fetch = refs/heads/*:refs/remote/origin/*
	[branch "master"]
		remote = origin
		merge = refs/heads/master
	[branch "develop/with/topics"]
		remote = origin
		merge = refs/heads/develop/with/topics
	...

	$ git for-each-ref \
		--format='%(push) %(push:remote-ref)' \
		refs/heads
	refs/remotes/origin/master refs/heads/master
	refs/remotes/origin/develop/with/topics refs/heads/develop/with/topics
---
 Documentation/git-for-each-ref.txt | 11 ++++++-----
 ref-filter.c                       | 12 +++++++++++-
 remote.c                           | 30 ++++++++++++++++++++++++++++++
 remote.h                           |  2 ++
 4 files changed, 49 insertions(+), 6 deletions(-)

diff --git a/Documentation/git-for-each-ref.txt b/Documentation/git-for-each-ref.txt
index 776368ee531..ba1147a1223 100644
--- a/Documentation/git-for-each-ref.txt
+++ b/Documentation/git-for-each-ref.txt
@@ -141,8 +141,9 @@ upstream::
 	also prints "[gone]" whenever unknown upstream ref is
 	encountered. Append `:track,nobracket` to show tracking
 	information without brackets (i.e "ahead N, behind M").  Also
-	respects `:remote-name` to state the name of the *remote* instead of
-	the ref.
+	respects `:remote-name` to state the name of the *remote* instead
+	of the ref, and `:remote-ref` to state the name of the *reference*
+	as locally known by the remote.
 +
 Has no effect if the ref does not have tracking information associated
 with it.  All the options apart from `nobracket` are mutually exclusive,
@@ -151,9 +152,9 @@ but if used together the last option is selected.
 push::
 	The name of a local ref which represents the `@{push}`
 	location for the displayed ref. Respects `:short`, `:lstrip`,
-	`:rstrip`, `:track`, `:trackshort` and `:remote-name` options as
-	`upstream` does. Produces an empty string if no `@{push}` ref is
-	configured.
+	`:rstrip`, `:track`, `:trackshort`, `:remote-name`, and `:remote-ref`
+	options as `upstream` does. Produces an empty string if no `@{push}`
+	ref is configured.
 
 HEAD::
 	'*' if HEAD matches current ref (the checked out branch), ' '
diff --git a/ref-filter.c b/ref-filter.c
index 58d53c09390..4401e573b8a 100644
--- a/ref-filter.c
+++ b/ref-filter.c
@@ -77,7 +77,7 @@ static struct used_atom {
 		struct align align;
 		struct {
 			enum {
-				RR_REF, RR_TRACK, RR_TRACKSHORT, RR_REMOTE_NAME
+				RR_REF, RR_TRACK, RR_TRACKSHORT, RR_REMOTE_NAME, RR_REMOTE_REF
 			} option;
 			struct refname_atom refname;
 			unsigned int nobracket : 1;
@@ -160,6 +160,8 @@ static void remote_ref_atom_parser(const struct ref_format *format, struct used_
 			atom->u.remote_ref.nobracket = 1;
 		else if (!strcmp(s, "remote-name"))
 			atom->u.remote_ref.option = RR_REMOTE_NAME;
+		else if (!strcmp(s, "remote-ref"))
+			atom->u.remote_ref.option = RR_REMOTE_REF;
 		else {
 			atom->u.remote_ref.option = RR_REF;
 			refname_atom_parser_internal(&atom->u.remote_ref.refname,
@@ -1260,6 +1262,14 @@ static void fill_remote_ref_details(struct used_atom *atom, const char *refname,
 			*s = xstrdup(remote);
 		else
 			*s = "";
+	} else if (atom->u.remote_ref.option == RR_REMOTE_REF) {
+		int explicit, for_push = starts_with(atom->name, "push");
+		const char *merge = remote_ref_for_branch(branch, for_push,
+							  &explicit);
+		if (explicit)
+			*s = xstrdup(merge);
+		else
+			*s = "";
 	} else
 		die("BUG: unhandled RR_* enum");
 }
diff --git a/remote.c b/remote.c
index b220f0dfc61..2bdcfc280cd 100644
--- a/remote.c
+++ b/remote.c
@@ -675,6 +675,36 @@ const char *pushremote_for_branch(struct branch *branch, int *explicit)
 	return remote_for_branch(branch, explicit);
 }
 
+const char *remote_ref_for_branch(struct branch *branch, int for_push,
+				  int *explicit)
+{
+	if (branch) {
+		if (!for_push) {
+			if (branch->merge_nr) {
+				if (explicit)
+					*explicit = 1;
+				return branch->merge_name[0];
+			}
+		} else {
+			const char *dst, *remote_name =
+				pushremote_for_branch(branch, NULL);
+			struct remote *remote = remote_get(remote_name);
+
+			if (remote && remote->push_refspec_nr &&
+			    (dst = apply_refspecs(remote->push,
+						  remote->push_refspec_nr,
+						  branch->refname))) {
+				if (explicit)
+					*explicit = 1;
+				return dst;
+			}
+		}
+	}
+	if (explicit)
+		*explicit = 0;
+	return "";
+}
+
 static struct remote *remote_get_1(const char *name,
 				   const char *(*get_default)(struct branch *, int *))
 {
diff --git a/remote.h b/remote.h
index 2ecf4c8c74c..1f6611be214 100644
--- a/remote.h
+++ b/remote.h
@@ -223,6 +223,8 @@ struct branch {
 struct branch *branch_get(const char *name);
 const char *remote_for_branch(struct branch *branch, int *explicit);
 const char *pushremote_for_branch(struct branch *branch, int *explicit);
+const char *remote_ref_for_branch(struct branch *branch, int for_push,
+				  int *explicit);
 
 int branch_has_merge_config(struct branch *branch);
 int branch_merge_matches(struct branch *, int n, const char *);
-- 
2.14.2.windows.1