checkstyle: Introduce a Commit class

This introduces a Commit class used in the final revlist list. All the
git commands are moved into that class. This class will be used to
introduce new types of commit (StagedChanges and Amendment) needed to implement
pre-commit hook support.

Signed-off-by: Nicolas Dufresne <nicolas.dufresne@collabora.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

utils/checkstyle.py

@@ -458,12 +458,33 @@ class StripTrailingSpaceFormatter(Formatter):
 # Style checking
 #
 
+class Commit:
+    def __init__(self, commit):
+        self.commit = commit
+
+    def get_info(self):
+        # Get the commit title and list of files.
+        ret = subprocess.run(['git', 'show', '--pretty=oneline', '--name-only',
+                              self.commit],
+                             stdout=subprocess.PIPE).stdout.decode('utf-8')
+        files = ret.splitlines()
+        # Returning title and files list as a tuple
+        return files[0], files[1:]
+
+    def get_diff(self, top_level, filename):
+        return subprocess.run(['git', 'diff', '%s~..%s' % (self.commit, self.commit),
+                               '--', '%s/%s' % (top_level, filename)],
+                              stdout=subprocess.PIPE).stdout.decode('utf-8')
+
+    def get_file(self, filename):
+        return subprocess.run(['git', 'show', '%s:%s' % (self.commit, filename)],
+                              stdout=subprocess.PIPE).stdout.decode('utf-8')
+
+
 def check_file(top_level, commit, filename):
     # Extract the line numbers touched by the commit.
-    diff = subprocess.run(['git', 'diff', '%s~..%s' % (commit, commit), '--',
-                           '%s/%s' % (top_level, filename)],
-                          stdout=subprocess.PIPE).stdout
-    diff = diff.decode('utf-8').splitlines(True)
+    diff = commit.get_diff(top_level, filename)
+    diff = diff.splitlines(True)
     commit_diff = parse_diff(diff)
 
     lines = []
@@ -476,9 +497,7 @@ def check_file(top_level, commit, filename):
 
     # Format the file after the commit with all formatters and compute the diff
     # between the unformatted and formatted contents.
-    after = subprocess.run(['git', 'show', '%s:%s' % (commit, filename)],
-                           stdout=subprocess.PIPE).stdout
-    after = after.decode('utf-8')
+    after = commit.get_file(filename)
 
     formatted = after
     for formatter in Formatter.formatters(filename):
@@ -522,12 +541,7 @@ def check_file(top_level, commit, filename):
 
 
 def check_style(top_level, commit):
-    # Get the commit title and list of files.
-    ret = subprocess.run(['git', 'show', '--pretty=oneline','--name-only', commit],
-                         stdout=subprocess.PIPE)
-    files = ret.stdout.decode('utf-8').splitlines()
-    title = files[0]
-    files = files[1:]
+    title, files = commit.get_info()
 
     separator = '-' * len(title)
     print(separator)
@@ -557,7 +571,7 @@ def check_style(top_level, commit):
     return issues
 
 
-def extract_revlist(revs):
+def extract_commits(revs):
     """Extract a list of commits on which to operate from a revision or revision
     range.
     """
@@ -576,7 +590,7 @@ def extract_revlist(revs):
         revlist = ret.stdout.decode('utf-8').splitlines()
         revlist.reverse()
 
-    return revlist
+    return [Commit(x) for x in revlist]
 
 
 def git_top_level():
@@ -632,10 +646,10 @@ def main(argv):
     if top_level is None:
             return 1
 
-    revlist = extract_revlist(args.revision_range)
+    commits = extract_commits(args.revision_range)
 
     issues = 0
-    for commit in revlist:
+    for commit in commits:
         issues += check_style(top_level, commit)
         print('')