1 # Copyright 2014 Google Inc. 2 # 3 # Use of this source code is governed by a BSD-style license that can be 4 # found in the LICENSE file. 5 6 """Module to host the ChangeGitBranch class and test_git_executable function. 7 """ 8 9 import os 10 import subprocess 11 12 import misc_utils 13 14 15 class ChangeGitBranch(object): 16 """Class to manage git branches. 17 18 This class allows one to create a new branch in a repository based 19 off of a given commit, and restore the original tree state. 20 21 Assumes current working directory is a git repository. 22 23 Example: 24 with ChangeGitBranch(): 25 edit_files(files) 26 git_add(files) 27 git_commit() 28 git_format_patch('HEAD~') 29 # At this point, the repository is returned to its original 30 # state. 31 32 Constructor Args: 33 branch_name: (string) if not None, the name of the branch to 34 use. If None, then use a temporary branch that will be 35 deleted. If the branch already exists, then a different 36 branch name will be created. Use git_branch_name() to 37 find the actual branch name used. 38 upstream_branch: (string) if not None, the name of the branch or 39 commit to branch from. If None, then use origin/master 40 verbose: (boolean) if true, makes debugging easier. 41 42 Raises: 43 OSError: the git executable disappeared. 44 subprocess.CalledProcessError: git returned unexpected status. 45 Exception: if the given branch name exists, or if the repository 46 isn't clean on exit, or git can't be found. 47 """ 48 # pylint: disable=I0011,R0903,R0902 49 50 def __init__(self, 51 branch_name=None, 52 upstream_branch=None, 53 verbose=False): 54 # pylint: disable=I0011,R0913 55 if branch_name: 56 self._branch_name = branch_name 57 self._delete_branch = False 58 else: 59 self._branch_name = 'ChangeGitBranchTempBranch' 60 self._delete_branch = True 61 62 if upstream_branch: 63 self._upstream_branch = upstream_branch 64 else: 65 self._upstream_branch = 'origin/master' 66 67 self._git = git_executable() 68 if not self._git: 69 raise Exception('Git can\'t be found.') 70 71 self._stash = None 72 self._original_branch = None 73 self._vsp = misc_utils.VerboseSubprocess(verbose) 74 75 def _has_git_diff(self): 76 """Return true iff repository has uncommited changes.""" 77 return bool(self._vsp.call([self._git, 'diff', '--quiet', 'HEAD'])) 78 79 def _branch_exists(self, branch): 80 """Return true iff branch exists.""" 81 return 0 == self._vsp.call([self._git, 'show-ref', '--quiet', branch]) 82 83 def __enter__(self): 84 git, vsp = self._git, self._vsp 85 86 if self._branch_exists(self._branch_name): 87 i, branch_name = 0, self._branch_name 88 while self._branch_exists(branch_name): 89 i += 1 90 branch_name = '%s_%03d' % (self._branch_name, i) 91 self._branch_name = branch_name 92 93 self._stash = self._has_git_diff() 94 if self._stash: 95 vsp.check_call([git, 'stash', 'save']) 96 self._original_branch = git_branch_name(vsp.verbose) 97 vsp.check_call( 98 [git, 'checkout', '-q', '-b', 99 self._branch_name, self._upstream_branch]) 100 101 def __exit__(self, etype, value, traceback): 102 git, vsp = self._git, self._vsp 103 104 if self._has_git_diff(): 105 status = vsp.check_output([git, 'status', '-s']) 106 raise Exception('git checkout not clean:\n%s' % status) 107 vsp.check_call([git, 'checkout', '-q', self._original_branch]) 108 if self._stash: 109 vsp.check_call([git, 'stash', 'pop']) 110 if self._delete_branch: 111 assert self._original_branch != self._branch_name 112 vsp.check_call([git, 'branch', '-D', self._branch_name]) 113 114 115 def git_branch_name(verbose=False): 116 """Return a description of the current branch. 117 118 Args: 119 verbose: (boolean) makes debugging easier 120 121 Returns: 122 A string suitable for passing to `git checkout` later. 123 """ 124 git = git_executable() 125 vsp = misc_utils.VerboseSubprocess(verbose) 126 try: 127 full_branch = vsp.strip_output([git, 'symbolic-ref', 'HEAD']) 128 return full_branch.split('/')[-1] 129 except (subprocess.CalledProcessError,): 130 # "fatal: ref HEAD is not a symbolic ref" 131 return vsp.strip_output([git, 'rev-parse', 'HEAD']) 132 133 134 def test_git_executable(git): 135 """Test the git executable. 136 137 Args: 138 git: git executable path. 139 Returns: 140 True if test is successful. 141 """ 142 with open(os.devnull, 'w') as devnull: 143 try: 144 subprocess.call([git, '--version'], stdout=devnull) 145 except (OSError,): 146 return False 147 return True 148 149 150 def git_executable(): 151 """Find the git executable. 152 153 If the GIT_EXECUTABLE environment variable is set, that will 154 override whatever is found in the PATH. 155 156 If no suitable executable is found, return None 157 158 Returns: 159 A string suiable for passing to subprocess functions, or None. 160 """ 161 env_git = os.environ.get('GIT_EXECUTABLE') 162 if env_git and test_git_executable(env_git): 163 return env_git 164 for git in ('git', 'git.exe', 'git.bat'): 165 if test_git_executable(git): 166 return git 167 return None 168 169
