git-backport: support renamed .cc files in commit message.

The change can automatically update names for *.cc files that
are part of a backport.

contrib/ChangeLog:

	* git-backport.py: Support renaming of .cc files.

contrib/git-backport.py

@@ -20,7 +20,31 @@
 # Boston, MA 02110-1301, USA.
 
 import argparse
+import os
 import subprocess
+import tempfile
+
+script_folder = os.path.dirname(os.path.abspath(__file__))
+verify_script = os.path.join(script_folder,
+                             'gcc-changelog/git_check_commit.py')
+
+
+def replace_file_in_changelog(lines, filename):
+    if not filename.endswith('.cc'):
+        return
+
+    # consider all componenets of a path: gcc/ipa-icf.cc
+    while filename:
+        for i, line in enumerate(lines):
+            if filename in line:
+                line = line.replace(filename, filename[:-1])
+                lines[i] = line
+                return
+        parts = filename.split('/')
+        if len(parts) == 1:
+            return
+        filename = '/'.join(parts[1:])
+
 
 if __name__ == '__main__':
     parser = argparse.ArgumentParser(description='Backport a git revision.')
@@ -28,3 +52,27 @@ if __name__ == '__main__':
     args = parser.parse_args()
 
     subprocess.run('git cherry-pick -x %s' % args.revision, shell=True)
+
+    # Update commit message if change for a .cc file was taken
+    r = subprocess.run(f'{verify_script} HEAD', shell=True, encoding='utf8',
+                       stdout=subprocess.PIPE, stderr=subprocess.PIPE)
+    if r.returncode != 0:
+        lines = r.stdout.splitlines()
+        cmd = 'git show -s --format=%B'
+        commit_message = subprocess.check_output(cmd, shell=True,
+                                                 encoding='utf8').strip()
+        commit_message = commit_message.splitlines()
+
+        todo = [line for line in lines if 'unchanged file mentioned' in line]
+        for item in todo:
+            filename = item.split()[-1].strip('"')
+            replace_file_in_changelog(commit_message, filename)
+
+        with tempfile.NamedTemporaryFile('w', encoding='utf8',
+                                         delete=False) as w:
+            w.write('\n'.join(commit_message))
+            w.close()
+            subprocess.check_output(f'git commit --amend -F {w.name}',
+                                    shell=True, encoding='utf8')
+            os.unlink(w.name)
+            print(f'Commit message updated: {len(todo)} .cc file(s) changed.')