cmd: project: fix edge case when revision is a SHA

If the revision is a SHA, we cannot assume the clone command will
fetch anything valid, as the remote HEAD may not have been properly
initialized.

For safety in that case, run a checkout step to ensure the work tree
is properly set up.

Signed-off-by: Marti Bolivar <marti@foundries.io>

src/west/cmd/project.py

@@ -503,8 +503,15 @@ def _fetch(project):
 
         msg = 'Cloning (name-and-path)'
         cmd = 'clone'
-        if not _is_sha(project.revision):
+        if _is_sha(project.revision):
+            # If the project revision is a SHA and the remote repo's
+            # HEAD doesn't point to anything valid, the clone
+            # operation might fail to check anything out. In that
+            # case, make sure to check out the given revision.
+            checkout = True
+        else:
             cmd += ' --branch (revision)'
+            checkout = False
         if project.clone_depth:
             msg += ' with --depth (clone-depth)'
             cmd += ' --depth (clone-depth)'
@@ -513,6 +520,9 @@ def _fetch(project):
         _inf(project, msg)
         _git_base(project, cmd)
 
+        if checkout:
+            _checkout(project, project.revision)
+
     # Update manifest-rev branch
     _git(project,
          'update-ref refs/heads/(manifest-rev-branch) {}'.format(