CLI/git: add --format-version argument to init subcommand

This is primarily intended to support testing upward compatibility
with legacy repos.

doc/man1/notmuch-git.rst

@@ -125,13 +125,19 @@ Fetch changes from the remote repository.
 
 Show brief help for an `notmuch git` command.
 
-.. option:: init
+.. option:: init [--format-version=N]
 
 Create an empty `notmuch git` repository.
 
 This wraps 'git init' with a few extra steps to support subsequent
 status and commit commands.
 
+   .. describe:: --format-version=N
+
+   Create a repo in format version N. By default :any:`notmuch-git`
+   uses the highest supported version, which is the best choice for
+   most use-cases.
+
 .. option:: log [arg ...]
 
 A wrapper for 'git log'.

notmuch-git.py

@@ -46,7 +46,7 @@ _LOG.addHandler(_logging.StreamHandler())
 
 NOTMUCH_GIT_DIR = None
 TAG_PREFIX = None
-FORMAT_VERSION = 0
+FORMAT_VERSION = 1
 
 _HEX_ESCAPE_REGEX = _re.compile('%[0-9A-F]{2}')
 _TAG_DIRECTORY = 'tags/'
@@ -452,7 +452,7 @@ def fetch(remote=None):
     _git(args=args, wait=True)
 
 
-def init(remote=None):
+def init(remote=None,format_version=None):
     """
     Create an empty notmuch-git repository.
 
@@ -466,14 +466,26 @@ def init(remote=None):
     except FileExistsError:
         pass
 
+    if not format_version:
+        format_version = 1
+
+    format_version=int(format_version)
+
+    if format_version > 1 or format_version < 0:
+        _LOG.error("Illegal format version {:d}".format(format_version))
+        _sys.exit(1)
+
     _spawn(args=['git', '--git-dir', NOTMUCH_GIT_DIR, 'init',
                  '--initial-branch=master', '--quiet', '--bare'], wait=True)
     _git(args=['config', 'core.logallrefupdates', 'true'], wait=True)
     # create an empty blob (e69de29bb2d1d6434b8b29ae775ad8c2e48c5391)
     _git(args=['hash-object', '-w', '--stdin'], input='', wait=True)
+    allow_empty=('--allow-empty',)
+    if format_version >= 1:
+        allow_empty=()
         # create a blob for the FORMAT file
         (status, stdout, _) = _git(args=['hash-object', '-w', '--stdin'], stdout=_subprocess.PIPE,
-                               input='1\n', wait=True)
+                                   input='{:d}\n'.format(format_version), wait=True)
         verhash=stdout.rstrip()
         _LOG.debug('hash of FORMAT blob = {:s}'.format(verhash))
         # Add FORMAT to the index
@@ -481,7 +493,7 @@ def init(remote=None):
 
     _git(
         args=[
-            'commit', '-m', 'Start a new notmuch-git repository'
+            'commit', *allow_empty, '-m', 'Start a new notmuch-git repository'
         ],
         additional_env={'GIT_WORK_TREE': NOTMUCH_GIT_DIR},
         wait=True)
@@ -1043,6 +1055,11 @@ if __name__ == '__main__':
             subparser.add_argument(
                 'command', metavar='COMMAND', nargs='?',
                 help='The command to show help for.')
+        elif command == 'init':
+            subparser.add_argument(
+                '--format-version', metavar='VERSION',
+                default = None,
+                help='create format VERSION repository.')
         elif command == 'log':
             subparser.add_argument(
                 'args', metavar='ARG', nargs='*',
@@ -1139,7 +1156,9 @@ if __name__ == '__main__':
     _LOG.debug('prefix = {:s}'.format(TAG_PREFIX))
     _LOG.debug('repository = {:s}'.format(NOTMUCH_GIT_DIR))
 
+    if args.func != init:
         FORMAT_VERSION = read_format_version()
+
     _LOG.debug('FORMAT_VERSION={:d}'.format(FORMAT_VERSION))
 
     if args.func == help:

test/T850-git.sh

@@ -347,4 +347,50 @@ prefix = test::
 EOF
 test_expect_equal_file EXPECTED OUTPUT
 
+test_begin_subtest "default version is 1"
+notmuch git -l debug -C default-version.git init
+output=$(git -C default-version.git cat-file blob HEAD:FORMAT)
+test_expect_equal "${output}" 1
+
+test_begin_subtest "illegal version"
+test_expect_code 1 "notmuch git -l debug -C default-version.git init --format-version=42"
+
+hash=("" "8d/c3/") # for use in synthetic repo contents.
+for ver in {0..1}; do
+    test_begin_subtest "init version=${ver}"
+    notmuch git -C version-${ver}.git  -p "test${ver}::" init --format-version=${ver}
+    output=$(git -C version-${ver}.git ls-tree -r --name-only HEAD)
+    expected=("" "FORMAT")
+    test_expect_equal "${output}" "${expected[${ver}]}"
+
+    test_begin_subtest "initial commit version=${ver}"
+    notmuch tag "+test${ver}::a" "+test${ver}::b" id:20091117190054.GU3165@dottiness.seas.harvard.edu
+    notmuch git -C version-${ver}.git -p "test${ver}::" commit --force
+    git -C version-${ver}.git ls-tree -r --name-only HEAD | grep -v FORMAT > OUTPUT
+cat <<EOF > EXPECTED
+tags/${hash[${ver}]}20091117190054.GU3165@dottiness.seas.harvard.edu/a
+tags/${hash[${ver}]}20091117190054.GU3165@dottiness.seas.harvard.edu/b
+EOF
+    test_expect_equal_file_nonempty EXPECTED OUTPUT
+
+    test_begin_subtest "second commit repo=${ver}"
+    notmuch tag "+test${ver}::c" "+test${ver}::d" id:20091117190054.GU3165@dottiness.seas.harvard.edu
+    notmuch git -C version-${ver}.git  -p "test${ver}::" commit --force
+    git -C version-${ver}.git ls-tree -r --name-only HEAD | grep -v FORMAT > OUTPUT
+cat <<EOF > EXPECTED
+tags/${hash[$ver]}20091117190054.GU3165@dottiness.seas.harvard.edu/a
+tags/${hash[$ver]}20091117190054.GU3165@dottiness.seas.harvard.edu/b
+tags/${hash[$ver]}20091117190054.GU3165@dottiness.seas.harvard.edu/c
+tags/${hash[$ver]}20091117190054.GU3165@dottiness.seas.harvard.edu/d
+EOF
+    test_expect_equal_file_nonempty EXPECTED OUTPUT
+
+    test_begin_subtest "checkout repo=${ver} "
+    notmuch dump > BEFORE
+    notmuch tag -test::${ver}::a '*'
+    notmuch git -C version-${ver}.git  -p "test${ver}::" checkout --force
+    notmuch dump > AFTER
+    test_expect_equal_file_nonempty BEFORE AFTER
+done
+
 test_done