init: support -b HEAD as a shortcut to "the default"

When people switch to non-default branches, they sometimes want to
switch back to the default, but don't know the exact name for that
branch.  Add a -b HEAD shortcut for that.

Change-Id: I090230da25f9f5a169608115d483f660f555624f
Reviewed-on: https://gerrit-review.googlesource.com/c/git-repo/+/297843
Reviewed-by: Michael Mortensen <mmortensen@google.com>
Tested-by: Mike Frysinger <vapier@google.com>

2 files changed, 10 insertions, 6 deletions

diff --git a/repo b/repo
index 1bc78b89..d32a84b9 100755
--- a/repo
+++ b/repo
@@ -289,8 +289,8 @@ def GetParser(gitc_init=False):
   group = parser.add_option_group('Manifest options')
   group.add_option('-u', '--manifest-url',
                    help='manifest repository location', metavar='URL')
-  group.add_option('-b', '--manifest-branch',
-                   help='manifest branch or revision', metavar='REVISION')
+  group.add_option('-b', '--manifest-branch', metavar='REVISION',
+                   help='manifest branch or revision (use HEAD for default)')
   group.add_option('-m', '--manifest-name',
                    help='initial manifest file', metavar='NAME.xml')
   cbr_opts = ['--current-branch']
diff --git a/subcmds/init.py b/subcmds/init.py
index ab0faff3..fc446045 100644
--- a/subcmds/init.py
+++ b/subcmds/init.py
@@ -48,7 +48,7 @@ argument.
 
 The optional -b argument can be used to select the manifest branch
 to checkout and use.  If no branch is specified, the remote's default
-branch is used.
+branch is used.  This is equivalent to using -b HEAD.
 
 The optional -m argument can be used to specify an alternate manifest
 to be used. If no manifest is specified, the manifest default.xml
@@ -94,9 +94,8 @@ to update the working directory files.
     g.add_option('-u', '--manifest-url',
                  dest='manifest_url',
                  help='manifest repository location', metavar='URL')
-    g.add_option('-b', '--manifest-branch',
-                 dest='manifest_branch',
-                 help='manifest branch or revision', metavar='REVISION')
+    g.add_option('-b', '--manifest-branch', metavar='REVISION',
+                 help='manifest branch or revision (use HEAD for default)')
     cbr_opts = ['--current-branch']
     # The gitc-init subcommand allocates -c itself, but a lot of init users
     # want -c, so try to satisfy both as best we can.
@@ -232,6 +231,11 @@ to update the working directory files.
       r.Save()
 
     if opt.manifest_branch:
+      if opt.manifest_branch == 'HEAD':
+        opt.manifest_branch = m.ResolveRemoteHead()
+        if opt.manifest_branch is None:
+          print('fatal: unable to resolve HEAD', file=sys.stderr)
+          sys.exit(1)
       m.revisionExpr = opt.manifest_branch
     else:
       if is_new: