A script that automatically reformat affected lines

Summary:
Added a script that reformat only the affected lines in a given diff.

I planned to make that file as pre-commit hook but looks it's a little bit more difficult than I thought. Since I don't want to spend too much time on this task right now, I eventually added a "make command" to achieve this with a few additional key strokes.

Also make the clang-format solely inherited from Google's style -- there are still debates on some of the style issues, but we can address them later once we reach a consensus.

Test Plan: Did some ugly format change and ran "make format", all affected lines are formatted as expected.

Reviewers: igor, sdong, haobo

CC: leveldb

Differential Revision: https://reviews.facebook.net/D15147

.clang-format

@@ -2,46 +2,4 @@
 # http://clang.llvm.org/docs/ClangFormatStyleOptions.html
 ---
 BasedOnStyle: Google
-AccessModifierOffset: -1
-ConstructorInitializerIndentWidth: 4
-AlignEscapedNewlinesLeft: true
-AlignTrailingComments: true
-AllowAllParametersOfDeclarationOnNextLine: true
-AllowShortIfStatementsOnASingleLine: false
-AllowShortLoopsOnASingleLine: false
-AlwaysBreakTemplateDeclarations: true
-AlwaysBreakBeforeMultilineStrings: true
-BreakBeforeBinaryOperators: false
-BreakConstructorInitializersBeforeComma: false
-BinPackParameters: false
-ColumnLimit:     80
-ConstructorInitializerAllOnOneLineOrOnePerLine: true
-DerivePointerBinding: true
-ExperimentalAutoDetectBinPacking: true
-IndentCaseLabels: false
-MaxEmptyLinesToKeep: 1
-NamespaceIndentation: None
-ObjCSpaceBeforeProtocolList: false
-PenaltyBreakBeforeFirstCallParameter: 10
-PenaltyBreakComment: 60
-PenaltyBreakString: 1000
-PenaltyBreakFirstLessLess: 20
-PenaltyExcessCharacter: 1000000
-PenaltyReturnTypeOnItsOwnLine: 200
-PointerBindsToType: true
-SpacesBeforeTrailingComments: 2
-Cpp11BracedListStyle: true
-Standard:        Cpp11
-IndentWidth:     2
-TabWidth:        8
-UseTab:          Never
-BreakBeforeBraces: Attach
-IndentFunctionDeclarationAfterType: false
-SpacesInParentheses: false
-SpacesInAngles: false
-SpaceInEmptyParentheses: false
-SpacesInCStyleCastParentheses: false
-SpaceAfterControlStatementKeyword: true
-SpaceBeforeAssignmentOperators: true
-ContinuationIndentWidth: 4
 ...

Makefile

@@ -135,7 +135,7 @@ endif  # PLATFORM_SHARED_EXT
 all: $(LIBRARY) $(PROGRAMS) $(SHARED)
 
 .PHONY: blackbox_crash_test check clean coverage crash_test ldb_tests \
-	release tags valgrind_check whitebox_crash_test
+	release tags valgrind_check whitebox_crash_test format
 
 release:
 	$(MAKE) clean
@@ -196,6 +196,9 @@ tags:
 	ctags * -R
 	cscope -b `find . -name '*.cc'` `find . -name '*.h'`
 
+format:
+	build_tools/format-diff.sh
+
 # ---------------------------------------------------------------------------
 # 	Unit tests and tools
 # ---------------------------------------------------------------------------
@@ -411,6 +414,12 @@ DEPFILES = $(filter-out util/build_version.d,$(SOURCES:.cc=.d))
 
 depend: $(DEPFILES)
 
+# if the make goal is either "clean" or "format", we shouldn't
+# try to import the *.d files.
+# TODO(kailiu) The unfamiliarity of Make's conditions leads to the ugly
+# working solution.
 ifneq ($(MAKECMDGOALS),clean)
+ifneq ($(MAKECMDGOALS),format)
 -include $(DEPFILES)
 endif
+endif

build_tools/format-diff.sh

@@ -0,0 +1,83 @@
+#!/bin/bash
+set -e
+# If clang_format_diff.py command is not specfied, we assume we are able to
+# access directly without any path.
+if [ -z $CLANG_FORMAT_DIFF ]
+then
+CLANG_FORMAT_DIFF="clang-format-diff.py"
+fi
+
+# Check clang-format-diff.py
+if ! which $CLANG_FORMAT_DIFF &> /dev/null
+then
+  echo "You didn't have clang-format-diff.py available in your computer!"
+  echo "You can download it by running: "
+  echo "    curl https://fburl.com/clang-format-diff"
+  exit 128
+fi
+
+# Check argparse, a library that clang-format-diff.py requires.
+python 2>/dev/null << EOF
+import argparse
+EOF
+
+if [ "$?" != 0 ]
+then
+  echo "To run clang-format-diff.py, we'll need the library "argparse" to be"
+  echo "installed. You can try either of the follow ways to install it:"
+  echo "  1. Manually download argparse: https://pypi.python.org/pypi/argparse"
+  echo "  2. easy_install argparse (if you have easy_install)"
+  echo "  3. pip install argparse (if you have pip)"
+  exit 129
+fi
+
+# TODO(kailiu) following work is not complete since we still need to figure
+# out how to add the modified files done pre-commit hook to git's commit index.
+#
+# Check if this script has already been added to pre-commit hook.
+# Will suggest user to add this script to pre-commit hook if their pre-commit
+# is empty.
+# PRE_COMMIT_SCRIPT_PATH="`git rev-parse --show-toplevel`/.git/hooks/pre-commit"
+# if ! ls $PRE_COMMIT_SCRIPT_PATH &> /dev/null
+# then
+#   echo "Would you like to add this script to pre-commit hook, which will do "
+#   echo -n "the format check for all the affected lines before you check in (y/n):"
+#   read add_to_hook
+#   if [ "$add_to_hook" == "y" ]
+#   then
+#     ln -s `git rev-parse --show-toplevel`/build_tools/format-diff.sh $PRE_COMMIT_SCRIPT_PATH
+#   fi
+# fi
+
+# Check the format of recently changed lines,
+diffs=$(git diff -U0 HEAD^ | $CLANG_FORMAT_DIFF -p 1)
+
+if [ -z "$diffs" ]
+then
+  echo "Nothing needs to be reformatted!"
+  exit 0
+fi
+
+# Highlight the insertion/deletion from the clang-format-diff.py's output
+COLOR_END="\033[0m"
+COLOR_RED="\033[0;31m" 
+COLOR_GREEN="\033[0;32m" 
+
+echo -e "Detect lines that doesn't follow the format rules:\r"
+# Add the color to the diff. lines added will be green; lines removed will be red.
+echo "$diffs" | 
+  sed -e "s/\(^-.*$\)/`echo -e \"$COLOR_RED\1$COLOR_END\"`/" |
+  sed -e "s/\(^+.*$\)/`echo -e \"$COLOR_GREEN\1$COLOR_END\"`/"
+echo -e "Would you like to fix the format automatically (y/n): \c"
+
+# Make sure under any mode, we can read user input.
+exec < /dev/tty
+read to_fix
+
+if [ "$to_fix" != "y" ]
+then
+  exit 1
+fi
+
+# Do in-place format adjustment.
+git diff -U0 HEAD^ | $CLANG_FORMAT_DIFF -i -p 1