tools: add .clang-format

Configuration for clang-format and related utilities.

Examples:

    clang-format -style=file <file>
    git clang-format -style=file <commit>
    git diff -U0 HEAD^ | clang-format-diff.py -i -p1 -style=file

CONTRIBUTING.md

@@ -68,6 +68,11 @@ For new code, please run [`clint.py`][clint] to detect style errors. It is not
 perfect and may have false positives and negatives. To have `clint.py` ignore
 certain special cases, put `// NOLINT` at the end of the line.
 
+We also provide a configuration file for [`clang-format` and 
+`git-clang-format`][clang-format], which can be used to format code according
+to the style guidelines. Be aware this formatting method might need user
+supervision.
+
 #### Commit guidelines
 
 The purpose of these guidelines is to *make reviews easier* and make the VCS logs more valuable.
@@ -93,6 +98,7 @@ The purpose of these guidelines is to *make reviews easier* and make the VCS log
 
 [cla]: https://docs.google.com/forms/d/1u54bpbwzneDIRltFx1TGi2evKxY3w0cOV3vlpj8DPbg/viewform
 [clint]: clint.py
+[clang-format]: http://clang.llvm.org/docs/ClangFormat.html
 [entry]: https://github.com/neovim/neovim/issues?labels=entry-level&state=open
 [imperative]: http://tbaggery.com/2008/04/19/a-note-about-git-commit-messages.html
 [style]: http://neovim.org/develop/style-guide.xml

src/.clang-format

@@ -0,0 +1,12 @@
+BasedOnStyle: llvm
+Language: Cpp
+ColumnLimit: 80
+IndentWidth: 2
+TabWidth: 2
+UseTab: Never
+IndentCaseLabels: true
+BreakBeforeBraces: Linux
+AlignEscapedNewlinesLeft: false
+AllowShortFunctionsOnASingleLine: false
+SpacesBeforeTrailingComments: 2
+PenaltyReturnTypeOnItsOwnLine: 200

src/nvim/version.c

@@ -177,6 +177,7 @@ static char *(features[]) = {
   NULL
 };
 
+// clang-format off
 static int included_patches[] = {
   //591 NA
   //590,
@@ -771,6 +772,7 @@ static int included_patches[] = {
   1,
   0
 };
+// clang-format on
 
 /// Place to put a short description when adding a feature with a patch.
 /// Keep it short, e.g.,: "relative numbers", "persistent undo".