builtin-remote: add set-head subcommand

Provide a porcelain command for setting and deleting
$GIT_DIR/remotes/<remote>/HEAD.

While we're at it, document what $GIT_DIR/remotes/<remote>/HEAD is all
about.

Signed-off-by: Jay Soffian <jaysoffian@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 26 insertions, 2 deletions

diff --git a/Documentation/git-remote.txt b/Documentation/git-remote.txt
index fad983e29..c9c0e6f93 100644
--- a/Documentation/git-remote.txt
+++ b/Documentation/git-remote.txt
@@ -13,6 +13,7 @@ SYNOPSIS
 'git remote add' [-t <branch>] [-m <master>] [-f] [--mirror] <name> <url>
 'git remote rename' <old> <new>
 'git remote rm' <name>
+'git remote set-head' <name> [-a | -d | <branch>]
 'git remote show' [-n] <name>
 'git remote prune' [-n | --dry-run] <name>
 'git remote update' [group]
@@ -53,8 +54,7 @@ is created.  You can give more than one `-t <branch>` to track
 multiple branches without grabbing all branches.
 +
 With `-m <master>` option, `$GIT_DIR/remotes/<name>/HEAD` is set
-up to point at remote's `<master>` branch instead of whatever
-branch the `HEAD` at the remote repository actually points at.
+up to point at remote's `<master>` branch. See also the set-head command.
 +
 In mirror mode, enabled with `\--mirror`, the refs will not be stored
 in the 'refs/remotes/' namespace, but in 'refs/heads/'.  This option
@@ -76,6 +76,30 @@ the configuration file format.
 Remove the remote named <name>. All remote tracking branches and
 configuration settings for the remote are removed.
 
+'set-head'::
+
+Sets or deletes the default branch (`$GIT_DIR/remotes/<name>/HEAD`) for
+the named remote. Having a default branch for a remote is not required,
+but allows the name of the remote to be specified in lieu of a specific
+branch. For example, if the default branch for `origin` is set to
+`master`, then `origin` may be specified wherever you would normally
+specify `origin/master`.
++
+With `-d`, `$GIT_DIR/remotes/<name>/HEAD` is deleted.
++
+With `-a`, the remote is queried to determine its `HEAD`, then
+`$GIT_DIR/remotes/<name>/HEAD` is set to the same branch. e.g., if the remote
+`HEAD` is pointed at `next`, "`git remote set-head origin -a`" will set
+`$GIT_DIR/refs/remotes/origin/HEAD` to `refs/remotes/origin/next`. This will
+only work if `refs/remotes/origin/next` already exists; if not it must be
+fetched first.
++
+Use `<branch>` to set `$GIT_DIR/remotes/<name>/HEAD` explicitly. e.g., "git
+remote set-head origin master" will set `$GIT_DIR/refs/remotes/origin/HEAD` to
+`refs/remotes/origin/master`. This will only work if
+`refs/remotes/origin/master` already exists; if not it must be fetched first.
++
+
 'show'::
 
 Gives some information about the remote <name>.