[PATCH v2 5/8] revision.c: better error reporting on ref from different worktrees

["Nguyễn Thái Ngọc Duy" <pclouds@gmail.com>]

Make use of the new ref aliases to pass refs from another worktree
around and access them from the current ref store instead. This does
not change any functionality, but when a problem arises, we would like
the reported messages to mention full ref aliases, like this:

    fatal: bad object worktrees/ztemp/HEAD
    warning: reflog of 'main-worktree/HEAD' references pruned commits

instead of

    fatal: bad object HEAD
    warning: reflog of 'HEAD' references pruned commits

which does not really tell where the refs are from.

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
---
 revision.c | 21 +++++++++++++--------
 worktree.c | 32 +++++++++++++++++++++++++++++---
 worktree.h | 14 ++++++++++++++
 3 files changed, 56 insertions(+), 11 deletions(-)

diff --git a/revision.c b/revision.c
index 63aae722c1..8ce660e3b1 100644
--- a/revision.c
+++ b/revision.c
@@ -1177,7 +1177,7 @@ struct all_refs_cb {
 	int warned_bad_reflog;
 	struct rev_info *all_revs;
 	const char *name_for_errormsg;
-	struct ref_store *refs;
+	struct worktree *wt;
 };
 
 int ref_excluded(struct string_list *ref_excludes, const char *path)
@@ -1214,7 +1214,7 @@ static void init_all_refs_cb(struct all_refs_cb *cb, struct rev_info *revs,
 	cb->all_revs = revs;
 	cb->all_flags = flags;
 	revs->rev_input_given = 1;
-	cb->refs = NULL;
+	cb->wt = NULL;
 }
 
 void clear_ref_exclusion(struct string_list **ref_excludes_p)
@@ -1277,15 +1277,20 @@ static int handle_one_reflog_ent(struct object_id *ooid, struct object_id *noid,
 	return 0;
 }
 
-static int handle_one_reflog(const char *refname,
+static int handle_one_reflog(const char *refname_in_wt,
 			     const struct object_id *oid,
 			     int flag, void *cb_data)
 {
 	struct all_refs_cb *cb = cb_data;
+	struct strbuf refname = STRBUF_INIT;
+
 	cb->warned_bad_reflog = 0;
-	cb->name_for_errormsg = refname;
-	refs_for_each_reflog_ent(cb->refs, refname,
+	strbuf_worktree_ref(cb->wt, &refname, refname_in_wt);
+	cb->name_for_errormsg = refname.buf;
+	refs_for_each_reflog_ent(get_main_ref_store(the_repository),
+				 refname.buf,
 				 handle_one_reflog_ent, cb_data);
+	strbuf_release(&refname);
 	return 0;
 }
 
@@ -1300,8 +1305,8 @@ static void add_other_reflogs_to_pending(struct all_refs_cb *cb)
 		if (wt->is_current)
 			continue;
 
-		cb->refs = get_worktree_ref_store(wt);
-		refs_for_each_reflog(cb->refs,
+		cb->wt = wt;
+		refs_for_each_reflog(get_worktree_ref_store(wt),
 				     handle_one_reflog,
 				     cb);
 	}
@@ -1314,7 +1319,7 @@ void add_reflogs_to_pending(struct rev_info *revs, unsigned flags)
 
 	cb.all_revs = revs;
 	cb.all_flags = flags;
-	cb.refs = get_main_ref_store(the_repository);
+	cb.wt = NULL;
 	for_each_reflog(handle_one_reflog, &cb);
 
 	if (!revs->single_worktree)
diff --git a/worktree.c b/worktree.c
index b0d0b5426d..ec1a5bc511 100644
--- a/worktree.c
+++ b/worktree.c
@@ -487,6 +487,28 @@ int submodule_uses_worktrees(const char *path)
 	return ret;
 }
 
+void strbuf_worktree_ref(const struct worktree *wt,
+			 struct strbuf *sb,
+			 const char *refname)
+{
+	if (wt && !wt->is_current) {
+		if (is_main_worktree(wt))
+			strbuf_addstr(sb, "main/");
+		else
+			strbuf_addf(sb, "worktrees/%s/", wt->id);
+	}
+	strbuf_addstr(sb, refname);
+}
+
+const char *worktree_ref(const struct worktree *wt, const char *refname)
+{
+	static struct strbuf sb = STRBUF_INIT;
+
+	strbuf_reset(&sb);
+	strbuf_worktree_ref(wt, &sb, refname);
+	return sb.buf;
+}
+
 int other_head_refs(each_ref_fn fn, void *cb_data)
 {
 	struct worktree **worktrees, **p;
@@ -495,13 +517,17 @@ int other_head_refs(each_ref_fn fn, void *cb_data)
 	worktrees = get_worktrees(0);
 	for (p = worktrees; *p; p++) {
 		struct worktree *wt = *p;
-		struct ref_store *refs;
+		struct object_id oid;
+		int flag;
 
 		if (wt->is_current)
 			continue;
 
-		refs = get_worktree_ref_store(wt);
-		ret = refs_head_ref(refs, fn, cb_data);
+		if (!refs_read_ref_full(get_main_ref_store(the_repository),
+					worktree_ref(wt, "HEAD"),
+					RESOLVE_REF_READING,
+					&oid, &flag))
+			ret = fn(worktree_ref(wt, "HEAD"), &oid, flag, cb_data);
 		if (ret)
 			break;
 	}
diff --git a/worktree.h b/worktree.h
index df3fc30f73..0016eb9e88 100644
--- a/worktree.h
+++ b/worktree.h
@@ -108,4 +108,18 @@ extern const char *worktree_git_path(const struct worktree *wt,
 				     const char *fmt, ...)
 	__attribute__((format (printf, 2, 3)));
 
+/*
+ * Return a refname suitable for access from the current ref store.
+ */
+void strbuf_worktree_ref(const struct worktree *wt,
+			 struct strbuf *sb,
+			 const char *refname);
+
+/*
+ * Return a refname suitable for access from the current ref
+ * store. The result may be destroyed at the next call.
+ */
+const char *worktree_ref(const struct worktree *wt,
+			 const char *refname);
+
 #endif
-- 
2.19.0.341.g3acb95d729