clang-format: Add an option to git-clang-format to diff between to commits

Summary:
When building pre-upload hooks using git-clang-format, it is useful to limit the scope to a diff of two commits (instead of from a commit against the working tree) to allow for less false positives in dependent commits.

This change adds the option of specifying two git commits to git-clang-format when using the `--diff` flag, which uses a different strategy to diff (using `git-diff-tree` instead of `git-diff-index`), and runs clang-format against the second commit instead of the working directory.

There is a slight backwards-incompatibility introduced with this change: if a filename matches a branch name or other commit-ish, then `git clang-format <commit> <file>` will no longer work as expected; use `git clang-format <commit> -- <file>` instead.

Patch by Luis Hector Chavez!

Reviewers: djasper, lodato

Subscribers: lodato, cfe-commits, srhines

Projects: #clang-c

Differential Revision: https://reviews.llvm.org/D24319

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@282136 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 97 insertions, 50 deletions

diff --git a/tools/clang-format/git-clang-format b/tools/clang-format/git-clang-format
index 860548e71e..ffa14368b6 100755
--- a/tools/clang-format/git-clang-format
+++ b/tools/clang-format/git-clang-format
@@ -32,12 +32,15 @@ import re
 import subprocess
 import sys
 
-usage = 'git clang-format [OPTIONS] [<commit>] [--] [<file>...]'
+usage = 'git clang-format [OPTIONS] [<commit>] [<commit>] [--] [<file>...]'
 
 desc = '''
-Run clang-format on all lines that differ between the working directory
-and <commit>, which defaults to HEAD.  Changes are only applied to the working
-directory.
+If zero or one commits are given, run clang-format on all lines that differ
+between the working directory and <commit>, which defaults to HEAD.  Changes are
+only applied to the working directory.
+
+If two commits are given (requires --diff), run clang-format on all lines in the
+second <commit> that differ from the first <commit>.
 
 The following git-config settings set the default of the corresponding option:
   clangFormat.binary
@@ -121,8 +124,14 @@ def main():
   opts.verbose -= opts.quiet
   del opts.quiet
 
-  commit, files = interpret_args(opts.args, dash_dash, opts.commit)
-  changed_lines = compute_diff_and_extract_lines(commit, files)
+  commits, files = interpret_args(opts.args, dash_dash, opts.commit)
+  if len(commits) > 1:
+    if not opts.diff:
+      die('--diff is required when two commits are given')
+  else:
+    if len(commits) > 2:
+      die('at most two commits allowed; %d given' % len(commits))
+  changed_lines = compute_diff_and_extract_lines(commits, files)
   if opts.verbose >= 1:
     ignored_files = set(changed_lines)
   filter_by_extension(changed_lines, opts.extensions.lower().split(','))
@@ -142,10 +151,17 @@ def main():
   # The computed diff outputs absolute paths, so we must cd before accessing
   # those files.
   cd_to_toplevel()
-  old_tree = create_tree_from_workdir(changed_lines)
-  new_tree = run_clang_format_and_save_to_tree(changed_lines,
-                                               binary=opts.binary,
-                                               style=opts.style)
+  if len(commits) > 1:
+    old_tree = commits[1]
+    new_tree = run_clang_format_and_save_to_tree(changed_lines,
+                                                 revision=commits[1],
+                                                 binary=opts.binary,
+                                                 style=opts.style)
+  else:
+    old_tree = create_tree_from_workdir(changed_lines)
+    new_tree = run_clang_format_and_save_to_tree(changed_lines,
+                                                 binary=opts.binary,
+                                                 style=opts.style)
   if opts.verbose >= 1:
     print 'old tree:', old_tree
     print 'new tree:', new_tree
@@ -182,40 +198,41 @@ def load_git_config(non_string_options=None):
 
 
 def interpret_args(args, dash_dash, default_commit):
-  """Interpret `args` as "[commit] [--] [files...]" and return (commit, files).
+  """Interpret `args` as "[commits] [--] [files]" and return (commits, files).
 
   It is assumed that "--" and everything that follows has been removed from
   args and placed in `dash_dash`.
 
-  If "--" is present (i.e., `dash_dash` is non-empty), the argument to its
-  left (if present) is taken as commit.  Otherwise, the first argument is
-  checked if it is a commit or a file.  If commit is not given,
-  `default_commit` is used."""
+  If "--" is present (i.e., `dash_dash` is non-empty), the arguments to its
+  left (if present) are taken as commits.  Otherwise, the arguments are checked
+  from left to right if they are commits or files.  If commits are not given,
+  a list with `default_commit` is used."""
   if dash_dash:
     if len(args) == 0:
-      commit = default_commit
-    elif len(args) > 1:
-      die('at most one commit allowed; %d given' % len(args))
+      commits = [default_commit]
     else:
-      commit = args[0]
-    object_type = get_object_type(commit)
-    if object_type not in ('commit', 'tag'):
-      if object_type is None:
-        die("'%s' is not a commit" % commit)
-      else:
-        die("'%s' is a %s, but a commit was expected" % (commit, object_type))
+      commits = args
+    for commit in commits:
+      object_type = get_object_type(commit)
+      if object_type not in ('commit', 'tag'):
+        if object_type is None:
+          die("'%s' is not a commit" % commit)
+        else:
+          die("'%s' is a %s, but a commit was expected" % (commit, object_type))
     files = dash_dash[1:]
   elif args:
-    if disambiguate_revision(args[0]):
-      commit = args[0]
-      files = args[1:]
-    else:
-      commit = default_commit
-      files = args
+    commits = []
+    while args:
+      if not disambiguate_revision(args[0]):
+        break
+      commits.append(args.pop(0))
+    if not commits:
+      commits = [default_commit]
+    files = args
   else:
-    commit = default_commit
+    commits = [default_commit]
     files = []
-  return commit, files
+  return commits, files
 
 
 def disambiguate_revision(value):
@@ -243,9 +260,9 @@ def get_object_type(value):
   return stdout.strip()
 
 
-def compute_diff_and_extract_lines(commit, files):
+def compute_diff_and_extract_lines(commits, files):
   """Calls compute_diff() followed by extract_lines()."""
-  diff_process = compute_diff(commit, files)
+  diff_process = compute_diff(commits, files)
   changed_lines = extract_lines(diff_process.stdout)
   diff_process.stdout.close()
   diff_process.wait()
@@ -255,13 +272,17 @@ def compute_diff_and_extract_lines(commit, files):
   return changed_lines
 
 
-def compute_diff(commit, files):
-  """Return a subprocess object producing the diff from `commit`.
+def compute_diff(commits, files):
+  """Return a subprocess object producing the diff from `commits`.
 
   The return value's `stdin` file object will produce a patch with the
-  differences between the working directory and `commit`, filtered on `files`
-  (if non-empty).  Zero context lines are used in the patch."""
-  cmd = ['git', 'diff-index', '-p', '-U0', commit, '--']
+  differences between the working directory and the first commit if a single
+  one was specified, or the difference between both specified commits, filtered
+  on `files` (if non-empty).  Zero context lines are used in the patch."""
+  git_tool = 'diff-index'
+  if len(commits) > 1:
+    git_tool = 'diff-tree'
+  cmd = ['git', git_tool, '-p', '-U0'] + commits + ['--']
   cmd.extend(files)
   p = subprocess.Popen(cmd, stdin=subprocess.PIPE, stdout=subprocess.PIPE)
   p.stdin.close()
@@ -318,15 +339,17 @@ def create_tree_from_workdir(filenames):
   return create_tree(filenames, '--stdin')
 
 
-def run_clang_format_and_save_to_tree(changed_lines, binary='clang-format',
-                                      style=None):
+def run_clang_format_and_save_to_tree(changed_lines, revision=None,
+                                      binary='clang-format', style=None):
   """Run clang-format on each file and save the result to a git tree.
 
   Returns the object ID (SHA-1) of the created tree."""
   def index_info_generator():
     for filename, line_ranges in changed_lines.iteritems():
       mode = oct(os.stat(filename).st_mode)
-      blob_id = clang_format_to_blob(filename, line_ranges, binary=binary,
+      blob_id = clang_format_to_blob(filename, line_ranges,
+                                     revision=revision,
+                                     binary=binary,
                                      style=style)
       yield '%s %s\t%s' % (mode, blob_id, filename)
   return create_tree(index_info_generator(), '--index-info')
@@ -352,26 +375,42 @@ def create_tree(input_lines, mode):
     return tree_id
 
 
-def clang_format_to_blob(filename, line_ranges, binary='clang-format',
-                         style=None):
+def clang_format_to_blob(filename, line_ranges, revision=None,
+                         binary='clang-format', style=None):
   """Run clang-format on the given file and save the result to a git blob.
 
+  Runs on the file in `revision` if not None, or on the file in the working
+  directory if `revision` is None.
+
   Returns the object ID (SHA-1) of the created blob."""
-  clang_format_cmd = [binary, filename]
+  clang_format_cmd = [binary]
   if style:
     clang_format_cmd.extend(['-style='+style])
   clang_format_cmd.extend([
       '-lines=%s:%s' % (start_line, start_line+line_count-1)
       for start_line, line_count in line_ranges])
+  if revision:
+    clang_format_cmd.extend(['-assume-filename='+filename])
+    git_show_cmd = ['git', 'cat-file', 'blob', '%s:%s' % (revision, filename)]
+    git_show = subprocess.Popen(git_show_cmd, stdin=subprocess.PIPE,
+                                stdout=subprocess.PIPE)
+    git_show.stdin.close()
+    clang_format_stdin = git_show.stdout
+  else:
+    clang_format_cmd.extend([filename])
+    git_show = None
+    clang_format_stdin = subprocess.PIPE
   try:
-    clang_format = subprocess.Popen(clang_format_cmd, stdin=subprocess.PIPE,
+    clang_format = subprocess.Popen(clang_format_cmd, stdin=clang_format_stdin,
                                     stdout=subprocess.PIPE)
+    if clang_format_stdin == subprocess.PIPE:
+      clang_format_stdin = clang_format.stdin
   except OSError as e:
     if e.errno == errno.ENOENT:
       die('cannot find executable "%s"' % binary)
     else:
       raise
-  clang_format.stdin.close()
+  clang_format_stdin.close()
   hash_object_cmd = ['git', 'hash-object', '-w', '--path='+filename, '--stdin']
   hash_object = subprocess.Popen(hash_object_cmd, stdin=clang_format.stdout,
                                  stdout=subprocess.PIPE)
@@ -381,6 +420,8 @@ def clang_format_to_blob(filename, line_ranges, binary='clang-format',
     die('`%s` failed' % ' '.join(hash_object_cmd))
   if clang_format.wait() != 0:
     die('`%s` failed' % ' '.join(clang_format_cmd))
+  if git_show and git_show.wait() != 0:
+    die('`%s` failed' % ' '.join(git_show_cmd))
   return stdout.rstrip('\r\n')
 
 
@@ -419,7 +460,12 @@ def print_diff(old_tree, new_tree):
   # We use the porcelain 'diff' and not plumbing 'diff-tree' because the output
   # is expected to be viewed by the user, and only the former does nice things
   # like color and pagination.
-  subprocess.check_call(['git', 'diff', old_tree, new_tree, '--'])
+  #
+  # We also only print modified files since `new_tree` only contains the files
+  # that were modified, so unmodified files would show as deleted without the
+  # filter.
+  subprocess.check_call(['git', 'diff', '--diff-filter=M', old_tree, new_tree,
+                         '--'])
 
 
 def apply_changes(old_tree, new_tree, force=False, patch_mode=False):
@@ -427,7 +473,8 @@ def apply_changes(old_tree, new_tree, force=False, patch_mode=False):
 
   Bails if there are local changes in those files and not `force`.  If
   `patch_mode`, runs `git checkout --patch` to select hunks interactively."""
-  changed_files = run('git', 'diff-tree', '-r', '-z', '--name-only', old_tree,
+  changed_files = run('git', 'diff-tree', '--diff-filter=M', '-r', '-z',
+                      '--name-only', old_tree,
                       new_tree).rstrip('\0').split('\0')
   if not force:
     unstaged_files = run('git', 'diff-files', '--name-status', *changed_files)