lorry: Use a working tree in gitify_cvs

Sadly, git cvsimport requires a working tree for most operations, and
only an initial import can be done successfully with the '-i' option.
Rather than adding back general support for non-bare repositories:

* When creating a mirror, let git cvsimport create it non-bare
  and then convert it to be bare
* When updating a mirror, add a temporary working tree with
  "git worktree add"

1 files changed, 55 insertions, 8 deletions

diff --git a/lorry b/lorry
index a3b42e0..81fdeb3 100755
--- a/lorry
+++ b/lorry
@@ -676,21 +676,68 @@ class Lorry(cliapp.Application):
         self.run_program(['git', 'svn', 'fetch'], cwd=gitdir)
 
     def gitify_cvs(self, project_name, dirname, gitdir, spec):
+        # git cvsimport requires a working tree for some operations;
+        # keep this separate from the repository
+        worktree = os.path.join(dirname, 'git-cvs-worktree')
+
+        if os.path.exists(gitdir):
+            if os.path.exists(worktree):
+                shutil.rmtree(worktree)
+            self.run_program(['git', 'worktree', 'prune'],
+                             cwd=gitdir)
+            self.run_program(['git', 'worktree', 'add', worktree, 'master'],
+                             cwd=gitdir)
+
+            # git cvsimport insists on $GIT_DIR or .git being a
+            # directory, but .git will be a file.  Set $GIT_DIR to
+            # the subdirectory of gitdir created for this worktree.
+            cvsimp_gitdir = self.runcmd(['git', 'rev-parse', '--git-dir'],
+                                        cwd=worktree) \
+                                .decode('utf-8') \
+                                .rstrip('\n')
+
+            # cvsps should find its cache under gitdir, not the
+            # temporary worktree
+            cvsps_home = gitdir
+        else:
+            # We must let git cvsimport create the repository
+            cvsimp_gitdir = os.path.join(worktree, '.git')
+
+            # cvsps should create its cache there, and it will be
+            # moved to gitdir later
+            cvsps_home = cvsimp_gitdir
+
         self.needs_aggressive = True
         env = dict(os.environ)
         env['CVS_RSH'] = 'lorry-ssh-wrapper'
-        env['GIT_DIR'] = gitdir
-        env['HOME'] = gitdir  # make cvsps store cache under git dir
+        env['GIT_DIR'] = cvsimp_gitdir
+        env['HOME'] = cvsps_home
         self.run_program(
             ['git', 'cvsimport', '-a', '-d', spec['url'],
-             '-i', spec['module']],
+             '-C', worktree, spec['module']],
             env=env)
 
-        # git cvsimport may create an index even in a bare repo
-        try:
-            os.remove(os.path.join(gitdir, 'index'))
-        except FileNotFoundError:
-            pass
+        if not os.path.exists(gitdir):
+            # git cvsimport created a non-bare repository; convert it
+            # to bare
+            os.rename(cvsimp_gitdir, gitdir)
+            self.run_program(['git', 'config', 'core.bare', 'true'],
+                             cwd=gitdir)
+            self.run_program(['git', 'config', 'core.logallrefupdates',
+                              'false'],
+                             cwd=gitdir)
+            try:
+                os.remove(os.path.join(gitdir, 'index'))
+            except FileNotFoundError:
+                pass
+            try:
+                shutil.rmtree(os.path.join(gitdir, 'logs'))
+            except FileNotFoundError:
+                pass
+
+        shutil.rmtree(worktree)
+        self.run_program(['git', 'worktree', 'prune'],
+                         cwd=gitdir)
 
     def gitify_hg(self, project_name, dirname, gitdir, spec):
         cert_options = []