utils: add common function to check out a specific git revision

Checking out a revision in the bitbake/layer repositories is something
we are doing in a few places, so add a checkout_repo() function that
does this, ensuring that we don't get tripped up by any junk files,
and avoids checking out if the repository is already at the desired
revision (thus avoiding the clean operation and e.g. preserving any
.pyc files that aren't stale and would speed things up a little). Note
that we do the clean before checking out in case there are untracked
files that are tracked in the commit we are checking out.

In addition to adding this function, change the existing code that we
use in the update script to check out a layer use the new function.

Signed-off-by: Paul Eggleton <paul.eggleton@linux.intel.com>

layerindex/recipeparse.py

@@ -31,8 +31,7 @@ def init_parser(settings, branch, bitbakepath, enable_tracking=False, nocheckout
         else:
             # Branch name
             bitbake_ref = 'origin/%s' % branch.bitbake_branch
-        out = utils.runcmd("git checkout %s" % bitbake_ref, bitbakepath, logger=logger)
+        utils.checkout_repo(bitbakepath, bitbake_ref, logger=logger)
-        out = utils.runcmd("git clean -f -x", bitbakepath, logger=logger)
 
     # Skip sanity checks
     os.environ['BB_ENV_EXTRAWHITE'] = 'DISABLE_SANITY_CHECKS'
@@ -57,8 +56,7 @@ def init_parser(settings, branch, bitbakepath, enable_tracking=False, nocheckout
         core_repodir = os.path.join(fetchdir, core_urldir)
         core_layerdir = os.path.join(core_repodir, core_subdir)
         if not nocheckout:
-            out = utils.runcmd("git checkout origin/%s" % core_branchname, core_repodir, logger=logger)
+            utils.checkout_repo(core_repodir, "origin/%s" % core_branchname, logger=logger)
-            out = utils.runcmd("git clean -f -x", core_repodir, logger=logger)
         if not os.path.exists(os.path.join(core_layerdir, 'conf/bitbake.conf')):
             raise RecipeParseError("conf/bitbake.conf not found in core layer %s - is subdirectory set correctly?" % core_layer.name)
         # The directory above where this script exists should contain our conf/layer.conf,

layerindex/utils.py

@@ -206,14 +206,34 @@ def explode_dep_versions2(bitbakepath, deps):
     import bb.utils
     return bb.utils.explode_dep_versions2(deps)
 
-def checkout_layer_branch(layerbranch, repodir, logger=None):
+def checkout_repo(repodir, commit, logger, force=False):
+    """
+    Check out a revision in a repository, ensuring that untracked/uncommitted
+    files don't get in the way.
+    WARNING: this will throw away any untracked/uncommitted files in the repo,
+    so it is only suitable for use with repos where you don't care about such
+    things (which we don't for the layer repos that we use)
+    """
+    if force:
+        currentref = ''
+    else:
+        currentref = runcmd("git rev-parse HEAD", repodir, logger=logger).strip()
+    if currentref != commit:
+        # Reset in case there are added but uncommitted changes
+        runcmd("git reset --hard HEAD", repodir, logger=logger)
+        # Drop any untracked files in case these cause problems (either because
+        # they will exist in the revision we're checking out, or will otherwise
+        # interfere with operation, e.g. stale pyc files)
+        runcmd("git clean -qdfx", repodir, logger=logger)
+        # Now check out the revision
+        runcmd("git checkout %s" % commit,
+                        repodir, logger=logger)
 
+def checkout_layer_branch(layerbranch, repodir, logger=None):
     branchname = layerbranch.branch.name
     if layerbranch.actual_branch:
         branchname = layerbranch.actual_branch
-
+    checkout_repo(repodir, 'origin/%s' % branchname, logger)
-    out = runcmd("git checkout origin/%s" % branchname, repodir, logger=logger)
-    out = runcmd("git clean -f -x", repodir, logger=logger)
 
 def is_layer_valid(layerdir):
     conf_file = os.path.join(layerdir, "conf", "layer.conf")