scripts/combo-layer: use last_revision if specified in init

If last_revision is specified for a component when running combo-layer
init, then use that revision instead of the latest revision on the
branch. Also, remove unnecessary git checkout during init since we
specify the revision to all calls to git when dealing with the component
repositories.

Fixes [YOCTO #3040].

(From OE-Core rev: ff8277cd133e9a02b131977078cff61fa587a1af)

Signed-off-by: Paul Eggleton <paul.eggleton@linux.intel.com>
Signed-off-by: Saul Wold <sgw@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

scripts/combo-layer

@@ -174,25 +174,31 @@ def action_init(conf, args):
         if not os.path.exists(ldir):
             logger.info("cloning %s to %s" %(conf.repos[name]['src_uri'], ldir))
             subprocess.check_call("git clone %s %s" % (conf.repos[name]['src_uri'], ldir), shell=True)
-        branch = conf.repos[name].get('branch', "master")
-        runcmd("git checkout %s" % branch, ldir)
     if not os.path.exists(".git"):
         runcmd("git init")
         for name in conf.repos:
             repo = conf.repos[name]
             ldir = repo['local_repo_dir']
-            logger.info("copying data from %s..." % name)
+            branch = repo.get('branch', "master")
+            lastrev = repo.get('last_revision', None)
+            if lastrev and lastrev != "HEAD":
+                initialrev = lastrev
+                logger.info("Copying data from %s at specified revision %s..." % (name, lastrev))
+            else:
+                lastrev = None
+                initialrev = branch
+                logger.info("Copying data from %s..." % name)
             dest_dir = repo['dest_dir']
             if dest_dir and dest_dir != ".":
                 extract_dir = os.path.join(os.getcwd(), dest_dir)
                 os.makedirs(extract_dir)
             else:
                 extract_dir = os.getcwd()
-            branch = repo.get('branch', "master")
             file_filter = repo.get('file_filter', "")
-            runcmd("git archive %s | tar -x -C %s %s" % (branch, extract_dir, file_filter), ldir)
-            lastrev = runcmd("git rev-parse %s" % branch, ldir).strip()
-            conf.update(name, "last_revision", lastrev, initmode=True)
+            runcmd("git archive %s | tar -x -C %s %s" % (initialrev, extract_dir, file_filter), ldir)
+            if not lastrev:
+                lastrev = runcmd("git rev-parse %s" % initialrev, ldir).strip()
+                conf.update(name, "last_revision", lastrev, initmode=True)
         runcmd("git add .")
         if conf.localconffile:
             localadded = True