[gnome-ostree] build: Avoid redoing patch checksums and checkouts unnecessarily

[Colin Walters <walters src gnome org>]

commit 24a6f1c5b572c1cd85d987f38ab59cb9b29aa874
Author: Colin Walters <walters verbum org>
Date:   Thu Sep 6 08:54:07 2012 -0400

    build: Avoid redoing patch checksums and checkouts unnecessarily
    
    Adding the patch checksums helped avoid rebuilding everything
    when we changed gnome-ostree, but we were recomputing the checksums
    of the current patches every time.  Fast path the case where
    the patch source hasn't changed revision.
    
    Also cache the patch checkout directory - if its revision hasn't
    changed, just reuse it.  This is always the case now.

 src/ostbuild/pyostbuild/builtin_build.py |   68 ++++++++++++++++-------------
 1 files changed, 37 insertions(+), 31 deletions(-)
---
diff --git a/src/ostbuild/pyostbuild/builtin_build.py b/src/ostbuild/pyostbuild/builtin_build.py
index 38d6bee..78c9d3e 100755
--- a/src/ostbuild/pyostbuild/builtin_build.py
+++ b/src/ostbuild/pyostbuild/builtin_build.py
@@ -122,22 +122,6 @@ class OstbuildBuild(builtins.Builtin):
         expanded_component = self.expand_component(component)
 
         skip_rebuild = self.args.compose_only
-        
-        if not skip_rebuild:
-            if 'patches' in expanded_component:
-                patchdir = vcs.checkout_patches(self.mirrordir,
-                                                self.patchdir,
-                                                expanded_component,
-                                                patches_path=self.args.patches_path)
-                patches_sha256sums = self._compute_sha256sums_for_patches(patchdir, expanded_component)
-                expanded_component['patches']['files_sha256sums'] = patches_sha256sums
-            else:
-                patchdir = None
-
-            force_rebuild = (self.buildopts.force_rebuild or
-                             basename in self.force_build_components)
-        else:
-            force_rebuild = False
 
         previous_build_version = run_sync_get_output(['ostree', '--repo=' + self.repo,
                                                       'rev-parse', build_ref],
@@ -150,30 +134,50 @@ class OstbuildBuild(builtins.Builtin):
             previous_metadata_text = run_sync_get_output(['ostree', '--repo=' + self.repo,
                                                           'cat', previous_build_version,
                                                           '/_ostbuild-meta.json'])
-            sha = hashlib.sha256()
-            sha.update(previous_metadata_text)
-
             previous_metadata = json.loads(previous_metadata_text)
             previous_vcs_version = previous_metadata.get('revision')
 
             log("Previous build of %s is ostree:%s " % (buildname, previous_build_version))
-
+        else:
+            log("No previous build for '%s' found" % (buildname, ))
             if skip_rebuild:
+                fatal("--compose-only specified but no previous build of %s found" % (buildname, ))
+            else:
                 return previous_build_version
 
-            rebuild_reason = self._needs_rebuild(previous_metadata, expanded_component)
-            if rebuild_reason is None:
-                if not force_rebuild:
-                    log("Reusing cached build at %s" % (previous_vcs_version)) 
-                    return previous_build_version
-                else:
-                    log("Build forced regardless") 
+        if 'patches' in expanded_component:
+            patches_revision = expanded_component['patches']['revision']
+            if self.cached_patchdir_revision == patches_revision:
+                patchdir = self.patchdir
             else:
-                    log("Need rebuild of %s: %s" % (buildname, rebuild_reason, ) )
+                patchdir = vcs.checkout_patches(self.mirrordir,
+                                                self.patchdir,
+                                                expanded_component,
+                                                patches_path=self.args.patches_path)
+                self.cached_patchdir_revision = patches_revision
+            if ((previous_metadata is not None) and
+                'patches' in previous_metadata and
+                previous_metadata['patches']['revision'] == patches_revision):
+                # Copy over the sha256sums
+                expanded_component['patches'] = previous_metadata['patches']
+            else:
+                patches_sha256sums = self._compute_sha256sums_for_patches(patchdir, expanded_component)
+                expanded_component['patches']['files_sha256sums'] = patches_sha256sums
         else:
-            log("No previous build for '%s' found" % (buildname, ))
-            if skip_rebuild:
-                fatal("--compose-only specified but no previous build found")
+            patchdir = None
+
+        force_rebuild = (self.buildopts.force_rebuild or
+                         basename in self.force_build_components)
+
+        rebuild_reason = self._needs_rebuild(previous_metadata, expanded_component)
+        if rebuild_reason is None:
+            if not force_rebuild:
+                log("Reusing cached build at %s" % (previous_vcs_version)) 
+                return previous_build_version
+            else:
+                log("Build forced regardless") 
+        else:
+                log("Need rebuild of %s: %s" % (buildname, rebuild_reason, ) )
 
         (fd, temp_metadata_path) = tempfile.mkstemp(suffix='.json', prefix='ostbuild-metadata-')
         os.close(fd)
@@ -379,6 +383,8 @@ class OstbuildBuild(builtins.Builtin):
 
         self.force_build_components = set()
 
+        self.cached_patchdir_revision = None
+
         components = self.snapshot['components']
 
         prefix = self.snapshot['prefix']