branch: move --set-upstream-to behavior to dwim_and_setup_tracking()

This commit is preparation for a future commit that will simplify
create_branch() so that it always creates a branch. This will allow
create_branch() to accept a dry_run parameter (which is needed for "git
branch --recurse-submodules").

create_branch() used to always create a branch, but 4fc5006676 (Add
branch --set-upstream, 2010-01-18) changed it to also be able to set
tracking information without creating a branch.

Refactor the code that sets tracking information into its own functions
dwim_branch_start() and dwim_and_setup_tracking(). Also change an
invocation of create_branch() in cmd_branch() in builtin/branch.c to use
dwim_and_setup_tracking(), since that invocation is only for setting
tracking information (in "git branch --set-upstream-to").

As of this commit, create_branch() is no longer invoked in a way that
does not create branches.

Helped-by: Jonathan Tan <jonathantanmy@google.com>
Signed-off-by: Glen Choo <chooglen@google.com>
Reviewed-by: Jonathan Tan <jonathantanmy@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 22 insertions, 0 deletions

diff --git a/branch.h b/branch.h
index 815dcd4..ab2315c 100644
--- a/branch.h
+++ b/branch.h
@@ -18,6 +18,28 @@ extern enum branch_track git_branch_track;
 
 /* Functions for acting on the information about branches. */
 
+/**
+ * Sets branch.<new_ref>.{remote,merge} config settings such that
+ * new_ref tracks orig_ref according to the specified tracking mode.
+ *
+ *   - new_ref is the name of the branch that we are setting tracking
+ *     for.
+ *
+ *   - orig_ref is the name of the ref that is 'upstream' of new_ref.
+ *     orig_ref will be expanded with DWIM so that the config settings
+ *     are in the correct format e.g. "refs/remotes/origin/main" instead
+ *     of "origin/main".
+ *
+ *   - track is the tracking mode e.g. BRANCH_TRACK_REMOTE causes
+ *     new_ref to track orig_ref directly, whereas BRANCH_TRACK_INHERIT
+ *     causes new_ref to track whatever orig_ref tracks.
+ *
+ *   - quiet suppresses tracking information.
+ */
+void dwim_and_setup_tracking(struct repository *r, const char *new_ref,
+			     const char *orig_ref, enum branch_track track,
+			     int quiet);
+
 /*
  * Creates a new branch, where:
  *