1 files changed, 29 insertions, 2 deletions

diff --git a/meta/classes/externalsrc.bbclass b/meta/classes/externalsrc.bbclass
index d3cede2b68..f98335980f 100644
--- a/meta/classes/externalsrc.bbclass
+++ b/meta/classes/externalsrc.bbclass
@@ -85,8 +85,10 @@ python () {
         d.prependVarFlag('do_compile', 'prefuncs', "externalsrc_compile_prefunc ")
         d.prependVarFlag('do_configure', 'prefuncs', "externalsrc_configure_prefunc ")
 
-        # Ensure compilation happens every time
-        d.setVarFlag('do_compile', 'nostamp', '1')
+        # Force the recipe to be always re-parsed so that the file_checksums
+        # function is run every time
+        d.setVar('BB_DONT_CACHE', '1')
+        d.setVarFlag('do_compile', 'file-checksums', '${@srctree_hash_files(d)}')
 
         # We don't want the workdir to go away
         d.appendVar('RM_WORK_EXCLUDE', ' ' + d.getVar('PN', True))
@@ -124,3 +126,28 @@ python externalsrc_compile_prefunc() {
     # Make it obvious that this is happening, since forgetting about it could lead to much confusion
     bb.plain('NOTE: %s: compiling from external source tree %s' % (d.getVar('PN', True), d.getVar('EXTERNALSRC', True)))
 }
+
+def srctree_hash_files(d):
+    import shutil
+    import subprocess
+
+    s_dir = d.getVar('EXTERNALSRC', True)
+    git_dir = os.path.join(s_dir, '.git')
+    oe_index_file = os.path.join(git_dir, 'oe-devtool-index')
+    oe_hash_file = os.path.join(git_dir, 'oe-devtool-tree-sha1')
+
+    ret = " "
+    if os.path.exists(git_dir):
+        # Clone index
+        shutil.copy2(os.path.join(git_dir, 'index'), oe_index_file)
+        # Update our custom index
+        env = os.environ.copy()
+        env['GIT_INDEX_FILE'] = oe_index_file
+        subprocess.check_output(['git', 'add', '.'], cwd=s_dir, env=env)
+        sha1 = subprocess.check_output(['git', 'write-tree'], cwd=s_dir, env=env)
+        with open(oe_hash_file, 'w') as fobj:
+            fobj.write(sha1)
+        ret = oe_hash_file + ':True'
+    else:
+        d.setVarFlag('do_compile', 'nostamp', '1')
+    return ret