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[PATCH 07/12] remote.c: add branch_get_push

From
Jeff King <peff@peff.net>
Date
May 1, 2015, 22:53 UTC
Message-ID
<20150501225331.GG1534@peff.net>
In-Reply-To
<20150501224414.GA25551@peff.net>

In a triangular workflow, the place you pull from and the place you push to may be different. As we have branch_get_upstream for the former, this patch adds branch_get_push for the latter (and as the former implements @{upstream}, so will this implement @{push} in a future patch).

Note that the memory-handling for the return value bears some explanation. Some code paths require allocating a new string, and some let us return an existing string. We should provide a consistent interface to the caller, so it knows whether to free the result or not.

We could do so by xstrdup-ing any existing strings, and having the caller always free. But that makes us inconsistent with branch_get_upstream, so we would prefer to simply take ownership of the resulting string. We do so by storing it inside the "struct branch", just as we do with the upstream refname (in that case we compute it when the branch is created, but there's no reason not to just fill it in lazily in this case).

Signed-off-by: Jeff King <peff@peff.net>
---
This patch is new in v2, but the logic is basically ripped from
sha1_name.c in v1.
 remote.c | 85 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 remote.h | 10 ++++++++
 2 files changed, 95 insertions(+)
diff --git a/remote.c b/remote.c
index 146b94d..7f0fe28 100644
--- a/remote.c
+++ b/remote.c
@@ -1727,6 +1727,91 @@ const char *branch_get_upstream(struct branch *branch, struct strbuf *err)
 	return branch->merge[0]->dst;
 }
 
+static const char *tracking_for_push_dest(struct remote *remote,
+					  const char *refname,
+					  struct strbuf *err)
+{
+	char *ret;
+
+	ret = apply_refspecs(remote->fetch, remote->fetch_refspec_nr, refname);
+	if (!ret)
+		return error_buf(err,
+				 _("push destination '%s' on remote '%s' has no local tracking branch"),
+				 refname, remote->name);
+	return ret;
+}
+
+static const char *branch_get_push_1(struct branch *branch, struct strbuf *err)
+{
+	struct remote *remote;
+
+	if (!branch)
+		return error_buf(err, _("HEAD does not point to a branch"));
+
+	remote = remote_get(pushremote_for_branch(branch, NULL));
+	if (!remote)
+		return error_buf(err,
+				 _("branch '%s' has no remote for pushing"),
+				 branch->name);
+
+	if (remote->push_refspec_nr) {
+		char *dst;
+		const char *ret;
+
+		dst = apply_refspecs(remote->push, remote->push_refspec_nr,
+				     branch->refname);
+		if (!dst)
+			return error_buf(err,
+					 _("push refspecs for '%s' do not include '%s'"),
+					 remote->name, branch->name);
+
+		ret = tracking_for_push_dest(remote, dst, err);
+		free(dst);
+		return ret;
+	}
+
+	if (remote->mirror)
+		return tracking_for_push_dest(remote, branch->refname, err);
+
+	switch (push_default) {
+	case PUSH_DEFAULT_NOTHING:
+		return error_buf(err, _("push has no destination (push.default is 'nothing')"));
+
+	case PUSH_DEFAULT_MATCHING:
+	case PUSH_DEFAULT_CURRENT:
+		return tracking_for_push_dest(remote, branch->refname, err);
+
+	case PUSH_DEFAULT_UPSTREAM:
+		return branch_get_upstream(branch, err);
+
+	case PUSH_DEFAULT_UNSPECIFIED:
+	case PUSH_DEFAULT_SIMPLE:
+		{
+			const char *up, *cur;
+
+			up = branch_get_upstream(branch, err);
+			if (!up)
+				return NULL;
+			cur = tracking_for_push_dest(remote, branch->refname, err);
+			if (!cur)
+				return NULL;
+			if (strcmp(cur, up))
+				return error_buf(err,
+						 _("cannot resolve 'simple' push to a single destination"));
+			return cur;
+		}
+	}
+
+	die("BUG: unhandled push situation");
+}
+
+const char *branch_get_push(struct branch *branch, struct strbuf *err)
+{
+	if (!branch->push_tracking_ref)
+		branch->push_tracking_ref = branch_get_push_1(branch, err);
+	return branch->push_tracking_ref;
+}
+
 static int ignore_symref_update(const char *refname)
 {
 	unsigned char sha1[20];
diff --git a/remote.h b/remote.h
index 03ca005..3326f2b 100644
--- a/remote.h
+++ b/remote.h
@@ -209,6 +209,8 @@ struct branch {
 	struct refspec **merge;
 	int merge_nr;
 	int merge_alloc;
+
+	const char *push_tracking_ref;
 };
 
 struct branch *branch_get(const char *name);
@@ -229,6 +231,14 @@ int branch_merge_matches(struct branch *, int n, const char *);
  */
 const char *branch_get_upstream(struct branch *branch, struct strbuf *err);
 
+/**
+ * Return the tracking branch that corresponds to the ref we would push to
+ * given a bare `git push` while `branch` is checked out.
+ *
+ * The return value and `err` conventions match those of `branch_get_upstream`.
+ */
+const char *branch_get_push(struct branch *branch, struct strbuf *err);
+
 /* Flags to match_refs. */
 enum match_refs_flags {
 	MATCH_REFS_NONE		= 0,

-- 
2.4.0.rc3.477.gc25258d
Previous: Jeff KingNext: Jeff King
Message 16 of 21 in “implement @{push} shorthand”
  1. 0/12 implement @{push} shorthandJeff King, May 1, 2015
  2. 01/12 remote.c: drop default_remote_name variableJeff King, May 1, 2015
  3. 02/12 remote.c: drop "remote" pointer from "struct branch"Jeff King, May 1, 2015
  4. Eric SunshineMay 3, 2015
  5. Jeff KingMay 5, 2015
  6. Jeff KingMay 7, 2015
  7. 03/12 remote.c: hoist branch.*.remote lookup out of remote_get_1Jeff King, May 1, 2015
  8. 04/12 remote.c: provide per-branch pushremote nameJeff King, May 1, 2015
  9. Eric SunshineMay 3, 2015
  10. Jeff KingMay 5, 2015
  11. Eric SunshineMay 5, 2015
  12. Jeff KingMay 7, 2015
  13. Eric SunshineMay 8, 2015
  14. 05/12 remote.c: introduce branch_get_upstream helperJeff King, May 1, 2015
  15. 06/12 remote.c: report specific errors from branch_get_upstreamJeff King, May 1, 2015
  16. 07/12 remote.c: add branch_get_pushJeff King, May 1, 2015
  17. 08/12 sha1_name: refactor upstream_markJeff King, May 1, 2015
  18. 09/12 sha1_name: refactor interpret_upstream_markJeff King, May 1, 2015
  19. 10/12 sha1_name: implement @{push} shorthandJeff King, May 1, 2015
  20. 11/12 for-each-ref: use skip_prefix instead of starts_withJeff King, May 1, 2015
  21. 12/12 for-each-ref: accept "%(push)" formatJeff King, May 1, 2015

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