project: abort a bit earlier before migrating .git/

Verify all the .git/ paths will be handled by the migration logic before
starting the migration.  This way we still abort & log an error, but the
user gets to see it before we put the tree into a state that they have to
manually recover.  Also add a few more known-safe-to-clobber paths.

Bug: https://crbug.com/gerrit/15273
Change-Id: If49d69b341bc960ddcafa30da333fb5ec7145b51
Reviewed-on: https://gerrit-review.googlesource.com/c/git-repo/+/327557
Reviewed-by: Colin Cross <ccross@android.com>
Tested-by: Mike Frysinger <vapier@google.com>

1 files changed, 27 insertions, 11 deletions

diff --git a/project.py b/project.py
index de593c83..48287858 100644
--- a/project.py
+++ b/project.py
@@ -2818,24 +2818,40 @@ class Project(object):
     }
     # Paths that we know will be in both, but are safe to clobber in .repo/projects/.
     SAFE_TO_CLOBBER = {
-        'COMMIT_EDITMSG', 'FETCH_HEAD', 'HEAD', 'index', 'ORIG_HEAD',
+        'COMMIT_EDITMSG', 'FETCH_HEAD', 'HEAD', 'gitk.cache', 'index', 'ORIG_HEAD',
     }
 
-    # Now walk the paths and sync the .git/ to .repo/projects/.
+    # First see if we'd succeed before starting the migration.
+    unknown_paths = []
     for name in platform_utils.listdir(dotgit):
+      # Ignore all temporary/backup names.  These are common with vim & emacs.
+      if name.endswith('~') or (name[0] == '#' and name[-1] == '#'):
+        continue
+
       dotgit_path = os.path.join(dotgit, name)
       if name in KNOWN_LINKS:
-        if platform_utils.islink(dotgit_path):
-          platform_utils.remove(dotgit_path)
-        else:
-          raise GitError(f'{dotgit_path}: should be a symlink')
+        if not platform_utils.islink(dotgit_path):
+          unknown_paths.append(f'{dotgit_path}: should be a symlink')
       else:
         gitdir_path = os.path.join(gitdir, name)
-        if name in SAFE_TO_CLOBBER or not os.path.exists(gitdir_path):
-          platform_utils.remove(gitdir_path, missing_ok=True)
-          platform_utils.rename(dotgit_path, gitdir_path)
-        else:
-          raise GitError(f'{dotgit_path}: unknown file; please file a bug')
+        if name not in SAFE_TO_CLOBBER and os.path.exists(gitdir_path):
+          unknown_paths.append(f'{dotgit_path}: unknown file; please file a bug')
+    if unknown_paths:
+      raise GitError('Aborting migration: ' + '\n'.join(unknown_paths))
+
+    # Now walk the paths and sync the .git/ to .repo/projects/.
+    for name in platform_utils.listdir(dotgit):
+      dotgit_path = os.path.join(dotgit, name)
+
+      # Ignore all temporary/backup names.  These are common with vim & emacs.
+      if name.endswith('~') or (name[0] == '#' and name[-1] == '#'):
+        platform_utils.remove(dotgit_path)
+      elif name in KNOWN_LINKS:
+        platform_utils.remove(dotgit_path)
+      else:
+        gitdir_path = os.path.join(gitdir, name)
+        platform_utils.remove(gitdir_path, missing_ok=True)
+        platform_utils.rename(dotgit_path, gitdir_path)
 
     # Now that the dir should be empty, clear it out, and symlink it over.
     platform_utils.rmdir(dotgit)