[PATCH 2/4] branch: add branch_checked_out() helper

["Derrick Stolee via GitGitGadget" <gitgitgadget@gmail.com>]

From: Derrick Stolee <derrickstolee@github.com>

The validate_new_branchname() method contains a check to see if a branch
is checked out in any non-bare worktree. This is intended to prevent a
force push that will mess up an existing checkout. This helper is not
suitable to performing just that check, because the method will die()
when the branch is checked out instead of returning an error code.

Extract branch_checked_out() and use it within
validate_new_branchname(). Another caller will be added in a coming
change.

Signed-off-by: Derrick Stolee <derrickstolee@github.com>
---
 branch.c | 24 ++++++++++++++++--------
 branch.h |  8 ++++++++
 2 files changed, 24 insertions(+), 8 deletions(-)

diff --git a/branch.c b/branch.c
index 2d6569b0c62..2e6419cdfa5 100644
--- a/branch.c
+++ b/branch.c
@@ -369,6 +369,19 @@ int validate_branchname(const char *name, struct strbuf *ref)
 	return ref_exists(ref->buf);
 }
 
+int branch_checked_out(const char *refname, char **path)
+{
+	struct worktree **worktrees = get_worktrees();
+	const struct worktree *wt = find_shared_symref(worktrees, "HEAD", refname);
+	int result = wt && !wt->is_bare;
+
+	if (result && path)
+		*path = xstrdup(wt->path);
+
+	free_worktrees(worktrees);
+	return result;
+}
+
 /*
  * Check if a branch 'name' can be created as a new branch; die otherwise.
  * 'force' can be used when it is OK for the named branch already exists.
@@ -377,9 +390,7 @@ int validate_branchname(const char *name, struct strbuf *ref)
  */
 int validate_new_branchname(const char *name, struct strbuf *ref, int force)
 {
-	struct worktree **worktrees;
-	const struct worktree *wt;
-
+	char *path;
 	if (!validate_branchname(name, ref))
 		return 0;
 
@@ -387,13 +398,10 @@ int validate_new_branchname(const char *name, struct strbuf *ref, int force)
 		die(_("a branch named '%s' already exists"),
 		    ref->buf + strlen("refs/heads/"));
 
-	worktrees = get_worktrees();
-	wt = find_shared_symref(worktrees, "HEAD", ref->buf);
-	if (wt && !wt->is_bare)
+	if (branch_checked_out(ref->buf, &path))
 		die(_("cannot force update the branch '%s' "
 		      "checked out at '%s'"),
-		    ref->buf + strlen("refs/heads/"), wt->path);
-	free_worktrees(worktrees);
+		    ref->buf + strlen("refs/heads/"), path);
 
 	return 1;
 }
diff --git a/branch.h b/branch.h
index 560b6b96a8f..5ea93d217b1 100644
--- a/branch.h
+++ b/branch.h
@@ -101,6 +101,14 @@ void create_branches_recursively(struct repository *r, const char *name,
 				 const char *tracking_name, int force,
 				 int reflog, int quiet, enum branch_track track,
 				 int dry_run);
+
+/*
+ * Returns true if the branch at 'refname' is checked out at any
+ * non-bare worktree. The path of the worktree is stored in the
+ * given 'path', if provided.
+ */
+int branch_checked_out(const char *refname, char **path);
+
 /*
  * Check if 'name' can be a valid name for a branch; die otherwise.
  * Return 1 if the named branch already exists; return 0 otherwise.
-- 
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