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+## Basic overview
+
+`./configure.py` generates the `build.ninja` files used to build
+ninja.  It accepts various flags to adjust build parameters.
+
+The primary build target of interest is `ninja`, but when hacking on
+Ninja your changes should be testable so it's more useful to build
+and run `ninja_test` when developing.
+
+(`./bootstrap.py` creates a bootstrap `ninja` and runs the above
+process; it's only necessary to run if you don't have a copy of
+`ninja` to build with.)
+
+### Adjusting build flags
+
+Build in "debug" mode while developing (disables optimizations and builds
+way faster on Windows):
+
+    ./configure.py --debug
+
+To use clang, set `CXX`:
+
+    CXX=clang++ ./configure.py
+
+## How to successfully make changes to Ninja
+
+Github pull requests are convenient for me to merge (I can just click
+a button and it's all handled server-side), but I'm also comfortable
+accepting pre-github git patches (via `send-email` etc.).
+
+Good pull requests have all of these attributes:
+
+* Are scoped to one specific issue
+* Include a test to demonstrate their correctness
+* Update the docs where relevant
+* Match the Ninja coding style (see below)
+* Don't include a mess of "oops, fix typo" commits
+
+These are typically merged without hesitation.  If a change is lacking
+any of the above I usually will ask you to fix it, though there are
+obvious exceptions (fixing typos in comments don't need tests).
+
+I am very wary of changes that increase the complexity of Ninja (in
+particular, new build file syntax or command-line flags) or increase
+the maintenance burden of Ninja.  Ninja is already successfully in use
+by hundreds of developers for large projects and it already achieves
+(most of) the goals I set out for it to do.  It's probably best to
+discuss new feature ideas on the mailing list before I shoot down your
+patch.
+
+## Testing
+
+### Installing gtest
+
+The `ninja_test` binary, containing all the tests, depends on the
+googletest (gtest) library.
+
+* On older Ubuntus it'll install as libraries into `/usr/lib`:
+
+        apt-get install libgtest
+
+* On newer Ubuntus it's only distributed as source
+
+        apt-get install libgtest-dev
+        ./configure.py --with-gtest=/usr/src/gtest
+
+* Otherwise you need to download it, unpack it, and pass
+  `--with-gtest` to `configure.py`.  Get it from [its downloads
+  page](http://code.google.com/p/googletest/downloads/list); [this
+  direct download link might work
+  too](http://googletest.googlecode.com/files/gtest-1.6.0.zip).
+
+### Test-driven development
+
+Set your build command to
+
+    ./ninja ninja_test && ./ninja_test --gtest_filter=MyTest.Name
+
+now you can repeatedly run that while developing until the tests pass
+(I frequently set it as my compilation command in Emacs).  Remember to
+build "all" before committing to verify the other source still works!
+
+## Testing performance impact of changes
+
+If you have a Chrome build handy, it's a good test case.  Otherwise,
+[the github downoads page](https://github.com/martine/ninja/downloads)
+has a copy of the Chrome build files (and depfiles). You can untar
+that, then run
+
+    path/to/my/ninja chrome
+
+and compare that against a baseline Ninja.
+
+There's a script at `misc/measure.py` that repeatedly runs a command like
+the above (to address variance) and summarizes its runtime.  E.g.
+
+    path/to/misc/measure.py path/to/my/ninja chrome
+
+For changing the depfile parser, you can also build `parser_perftest`
+and run that directly on some representative input files.
+
+## Coding guidelines
+
+Generally it's the [Google C++ coding style][], but in brief:
+
+* Function name are camelcase.
+* Member methods are camelcase, expect for trivial getters which are
+  underscore separated.
+* Local variables are underscore separated.
+* Member variables are underscore separated and suffixed by an extra
+  underscore.
+* Two spaces indentation.
+* Opening braces is at the end of line.
+* Lines are 80 columns maximum.
+* All source files should have the Google Inc. license header.
+
+[Google C++ coding style]: http://google-styleguide.googlecode.com/svn/trunk/cppguide.xml
+
+## Documentation
+
+### Style guidelines
+
+* Use `///` for doxygen.
+* Use `\a` to refer to arguments.
+* It's not necessary to document each argument, especially when they're
+  relatively self-evident (e.g. in `CanonicalizePath(string* path, string* err)`,
+  the arguments are hopefully obvious)
+
+### Building the manual
+
+    sudo apt-get install asciidoc --no-install-recommends
+    ./ninja manual
+
+### Building the code documentation
+
+    sudo apt-get install doxygen
+    ./ninja doxygen
+
+## Building for Windows
+
+While developing, it's helpful to copy `ninja.exe` to another name like
+`n.exe`; otherwise, rebuilds will be unable to write `ninja.exe` because
+it's locked while in use.
+
+### Via Visual Studio
+
+* Install Visual Studio (Express is fine), [Python for Windows][],
+  and (if making changes) googletest (see above instructions)
+* In a Visual Studio command prompt: `python bootstrap.py`
+
+[Python for Windows]: http://www.python.org/getit/windows/
+
+### Via mingw on Windows (not well supported)
+
+* Install mingw, msys, and python
+* In the mingw shell, put Python in your path, and `python bootstrap.py`
+* To reconfigure, run `python configure.py`
+* Remember to strip the resulting executable if size matters to you
+
+### Via mingw on Linux (not well supported)
+
+Setup on Ubuntu Lucid:
+* `sudo apt-get install gcc-mingw32 wine`
+* `export CC=i586-mingw32msvc-cc CXX=i586-mingw32msvc-c++ AR=i586-mingw32msvc-ar`
+
+Setup on Ubuntu Precise:
+* `sudo apt-get install gcc-mingw-w64-i686 g++-mingw-w64-i686 wine`
+* `export CC=i686-w64-mingw32-gcc CXX=i686-w64-mingw32-g++ AR=i686-w64-mingw32-ar`
+
+Then run:
+* `./configure.py --platform=mingw --host=linux`
+* Build `ninja.exe` using a Linux ninja binary: `/path/to/linux/ninja`
+* Run: `./ninja.exe`  (implicitly runs through wine(!))
+
+### Using Microsoft compilers on Linux (extremely flaky)
+
+The trick is to install just the compilers, and not all of Visual Studio,
+by following [these instructions][win7sdk].
+
+[win7sdk]: http://www.kegel.com/wine/cl-howto-win7sdk.html