1 files changed, 231 insertions, 0 deletions
diff --git a/repo/fun.py b/repo/fun.py
new file mode 100644
index 00000000..a0f66fe5
--- /dev/null
+++ b/repo/fun.py
@@ -0,0 +1,231 @@
+"""Package with general repository related functions"""
+
+from gitdb.exc import BadObject
+from git.refs import SymbolicReference
+from git.objects import Object
+from gitdb.util import (
+							join,
+							isdir, 
+							isfile,
+							hex_to_bin, 
+							bin_to_hex
+						)
+from string import digits
+
+__all__ = ('rev_parse', 'is_git_dir', 'touch')
+
+def touch(filename):
+	fp = open(filename, "a")
+	fp.close()
+
+def is_git_dir(d):
+	""" This is taken from the git setup.c:is_git_directory
+	function."""
+	if isdir(d) and \
+			isdir(join(d, 'objects')) and \
+			isdir(join(d, 'refs')):
+		headref = join(d, 'HEAD')
+		return isfile(headref) or \
+				(os.path.islink(headref) and
+				os.readlink(headref).startswith('refs'))
+	return False
+
+
+def short_to_long(odb, hexsha):
+	""":return: long hexadecimal sha1 from the given less-than-40 byte hexsha
+		or None if no candidate could be found.
+	:param hexsha: hexsha with less than 40 byte"""
+	try:
+		return bin_to_hex(odb.partial_to_complete_sha_hex(hexsha))
+	except BadObject:
+		return None
+	# END exception handling
+	
+	
+def name_to_object(repo, name):
+	""":return: object specified by the given name, hexshas ( short and long )
+		as well as references are supported"""
+	hexsha = None
+	
+	# is it a hexsha ? Try the most common ones, which is 7 to 40
+	if repo.re_hexsha_shortened.match(name):
+		if len(name) != 40:
+			# find long sha for short sha
+			hexsha = short_to_long(repo.odb, name)
+		else:
+			hexsha = name
+		# END handle short shas
+	else:
+		for base in ('%s', 'refs/%s', 'refs/tags/%s', 'refs/heads/%s', 'refs/remotes/%s', 'refs/remotes/%s/HEAD'):
+			try:
+				hexsha = SymbolicReference.dereference_recursive(repo, base % name)
+				break
+			except ValueError:
+				pass
+		# END for each base
+	# END handle hexsha
+	
+	# tried everything ? fail
+	if hexsha is None:
+		raise BadObject(name)
+	# END assert hexsha was found
+	
+	return Object.new_from_sha(repo, hex_to_bin(hexsha))
+
+def deref_tag(tag):
+	"""Recursively dereerence a tag and return the resulting object"""
+	while True:
+		try:
+			tag = tag.object
+		except AttributeError:
+			break
+	# END dereference tag
+	return tag
+
+def to_commit(obj):
+	"""Convert the given object to a commit if possible and return it"""
+	if obj.type == 'tag':
+		obj = deref_tag(obj)
+		
+	if obj.type != "commit":
+		raise ValueError("Cannot convert object %r to type commit" % obj)
+	# END verify type
+	return obj
+
+def rev_parse(repo, rev):
+	"""
+	:return: Object at the given revision, either Commit, Tag, Tree or Blob
+	:param rev: git-rev-parse compatible revision specification, please see
+		http://www.kernel.org/pub/software/scm/git/docs/git-rev-parse.html
+		for details
+	:note: Currently there is no access to the rev-log, rev-specs may only contain
+		topological tokens such ~ and ^.
+	:raise BadObject: if the given revision could not be found"""
+	if '@' in rev:
+		raise ValueError("There is no rev-log support yet")
+	
+	
+	# colon search mode ?
+	if rev.startswith(':/'):
+		# colon search mode
+		raise NotImplementedError("commit by message search ( regex )")
+	# END handle search
+	
+	obj = None
+	output_type = "commit"
+	start = 0
+	parsed_to = 0
+	lr = len(rev)
+	while start < lr:
+		if rev[start] not in "^~:":
+			start += 1
+			continue
+		# END handle start
+		
+		if obj is None:
+			# token is a rev name
+			obj = name_to_object(repo, rev[:start])
+		# END initialize obj on first token
+		
+		token = rev[start]
+		start += 1
+		
+		# try to parse {type}
+		if start < lr and rev[start] == '{':
+			end = rev.find('}', start)
+			if end == -1:
+				raise ValueError("Missing closing brace to define type in %s" % rev)
+			output_type = rev[start+1:end]	# exclude brace
+			
+			# handle type 
+			if output_type == 'commit':
+				pass # default
+			elif output_type == 'tree':
+				try:
+					obj = to_commit(obj).tree
+				except (AttributeError, ValueError):
+					pass	# error raised later
+				# END exception handling
+			elif output_type in ('', 'blob'):
+				if obj.type == 'tag':
+					obj = deref_tag(obj)
+				else:
+					# cannot do anything for non-tags
+					pass
+				# END handle tag
+			else:
+				raise ValueError("Invalid output type: %s ( in %s )"  % (output_type, rev))
+			# END handle output type
+			
+			# empty output types don't require any specific type, its just about dereferencing tags
+			if output_type and obj.type != output_type:
+				raise ValueError("Could not accomodate requested object type %r, got %s" % (output_type, obj.type))
+			# END verify ouput type
+			
+			start = end+1					# skip brace
+			parsed_to = start
+			continue
+		# END parse type
+		
+		# try to parse a number
+		num = 0
+		if token != ":":
+			found_digit = False
+			while start < lr:
+				if rev[start] in digits:
+					num = num * 10 + int(rev[start])
+					start += 1
+					found_digit = True
+				else:
+					break
+				# END handle number
+			# END number parse loop
+			
+			# no explicit number given, 1 is the default
+			# It could be 0 though 
+			if not found_digit:
+				num = 1
+			# END set default num
+		# END number parsing only if non-blob mode
+		
+		
+		parsed_to = start
+		# handle hiererarchy walk
+		try:
+			if token == "~":
+				obj = to_commit(obj)
+				for item in xrange(num):
+					obj = obj.parents[0]
+				# END for each history item to walk
+			elif token == "^":
+				obj = to_commit(obj)
+				# must be n'th parent
+				if num:
+					obj = obj.parents[num-1]
+			elif token == ":":
+				if obj.type != "tree":
+					obj = obj.tree
+				# END get tree type
+				obj = obj[rev[start:]]
+				parsed_to = lr
+			else:
+				raise ValueError("Invalid token: %r" % token)
+			# END end handle tag
+		except (IndexError, AttributeError):
+			raise BadObject("Invalid Revision in %s" % rev)
+		# END exception handling
+	# END parse loop
+	
+	# still no obj ? Its probably a simple name
+	if obj is None:
+		obj = name_to_object(repo, rev)
+		parsed_to = lr
+	# END handle simple name
+	
+	if obj is None:
+		raise ValueError("Revision specifier could not be parsed: %s" % rev)
+
+	if parsed_to != lr:
+		raise ValueError("Didn't consume complete rev spec %s, consumed part: %s" % (rev, rev[:parsed_to]))
+	
+	return obj