util: git pre-commit hook to check staged files

This patch updates the git-pre-commit hook to check the files as they
will be after the commit, instead of as they are currently, this way we
prevent the undesired situation:
    - unstylish modification of a file
    - stage said file for commit
    - try to commit and fail due to style
    - fix style, forgetting staging changes
    - try to commit and fail, as although the changes staged are not
      styly, the current content of the file is.

Change-Id: I5cc3f783375d9e4162e310e176103ebbf0a59023
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>
[andreas.sandberg@arm.com: Rebased ontop of latest gem5]

1 files changed, 33 insertions, 7 deletions

diff --git a/util/git-pre-commit.py b/util/git-pre-commit.py
index 480bba1c9..276e21fc5 100755
--- a/util/git-pre-commit.py
+++ b/util/git-pre-commit.py
@@ -37,7 +37,9 @@
 #
 # Authors: Andreas Sandberg
 
+from tempfile import TemporaryFile
 import os
+import subprocess
 import sys
 
 from style.repo import GitRepo
@@ -62,6 +64,7 @@ ui = StdioUI()
 
 os.chdir(repo_base)
 failing_files = set()
+staged_mismatch = set()
 
 for status, fname in git.status(filter="MA", cached=True):
     if args.verbose:
@@ -73,18 +76,41 @@ for status, fname in git.status(filter="MA", cached=True):
     else:
         regions = all_regions
 
+    # Show they appropriate object and dump it to a file
+    status = git.file_from_index(fname)
+    f = TemporaryFile()
+    f.write(status)
+
     verifiers = [ v(ui, opts, base=repo_base) for v in all_verifiers ]
     for v in verifiers:
-        if not v.skip(fname) and v.check(fname, regions):
+        f.seek(0)
+        # It is prefered that the first check is silent as it is in the
+        # staged file. If the check fails, then we will do it non-silently
+        # on the current file, reporting meaningful shortcomings
+        if not v.skip(fname) and v.check(fname, regions, fobj=f, silent=True):
             failing_files.add(fname)
+            if not v.check(fname, regions):
+                staged_mismatch.add(fname)
+    f.close()
 
 if failing_files:
-    print >> sys.stderr
-    print >> sys.stderr, "Style checker failed for the following files:"
-    for f in failing_files:
-        print >> sys.stderr, "\t%s" % f
-    print >> sys.stderr
-    print >> sys.stderr, \
+    if len(failing_files) > len(staged_mismatch):
+        print >> sys.stderr
+        print >> sys.stderr, "Style checker failed for the following files:"
+        for f in failing_files:
+            if f not in staged_mismatch:
+                print >> sys.stderr, "\t%s" % f
+        print >> sys.stderr
+        print >> sys.stderr, \
         "Please run the style checker manually to fix the offending files.\n" \
         "To check your modifications, run: util/style.py -m"
+
+    print >> sys.stderr
+    if staged_mismatch:
+        print >> sys.stderr, \
+        "It looks like you have forgotten to stage your fixes for commit in\n"\
+        "the following files: "
+        for f in staged_mismatch:
+            print >> sys.stderr, "\t%s" % f
+        print >> sys.stderr, "Please `git --add' them"
     sys.exit(1)