Add YCM config file for VIM users

Tailor-made for Mapbox GL Native.

For instructions of how to use, see:
https://github.com/Valloric/YouCompleteMe

.ycm_extra_conf.py

@@ -0,0 +1,123 @@
+# Adapted version of .ycm_extra_conf.py sample file adapted
+# for the Mapbox GL Native project.
+#
+# This file is NOT licensed under the GPLv3, which is the license for the rest
+# of YouCompleteMe.
+#
+# Here's the license text for this file:
+#
+# This is free and unencumbered software released into the public domain.
+#
+# Anyone is free to copy, modify, publish, use, compile, sell, or
+# distribute this software, either in source code form or as a compiled
+# binary, for any purpose, commercial or non-commercial, and by any
+# means.
+#
+# In jurisdictions that recognize copyright laws, the author or authors
+# of this software dedicate any and all copyright interest in the
+# software to the public domain. We make this dedication for the benefit
+# of the public at large and to the detriment of our heirs and
+# successors. We intend this dedication to be an overt act of
+# relinquishment in perpetuity of all present and future rights to this
+# software under copyright law.
+#
+# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+# EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+# MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
+# IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY CLAIM, DAMAGES OR
+# OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
+# ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
+# OTHER DEALINGS IN THE SOFTWARE.
+#
+# For more information, please refer to <http://unlicense.org/>
+
+import os
+import subprocess
+import sys
+import ycm_core
+
+
+def DirectoryOfThisScript():
+    return os.path.dirname(os.path.abspath(__file__))
+
+
+default_flags = [
+    '-std=c++14',
+    '-I%s' % (os.path.join(DirectoryOfThisScript(), 'src')),
+    '-I%s' % (os.path.join(DirectoryOfThisScript(), 'include')),
+]
+
+
+def MakeRelativePathsInFlagsAbsolute(flags, working_directory):
+    if not working_directory:
+        return list(flags)
+
+    new_flags = []
+    make_next_absolute = False
+    path_flags = ['-isystem', '-I', '-iquote', '--sysroot=']
+
+    for flag in flags:
+        new_flag = flag
+
+        if make_next_absolute:
+            make_next_absolute = False
+            if not flag.startswith('/'):
+                new_flag = os.path.join(working_directory, flag)
+
+        for path_flag in path_flags:
+            if flag == path_flag:
+                make_next_absolute = True
+                break
+
+            if flag.startswith(path_flag):
+                path = flag[len(path_flag):]
+                new_flag = path_flag + os.path.join(working_directory, path)
+                break
+
+        if new_flag:
+            new_flags.append(new_flag)
+
+    return new_flags
+
+
+def FlagsForFileLinux(filename):
+    working_directory = os.path.join('build', 'linux')
+
+    if not os.path.exists(os.path.join(DirectoryOfThisScript(), working_directory)):
+        return {
+            'flags': default_flags,
+            'do_cache': False,
+        }
+
+    relative_source_path = filename.replace(DirectoryOfThisScript() + '/', '')
+    relative_obj_path = os.path.splitext(relative_source_path)[0] + '.o'
+
+    make_cmd = 'make -pn |grep %s: |grep GYP_CXXFLAGS |cut -d\' \' -f4-' % relative_obj_path
+
+    p = subprocess.Popen([make_cmd], shell=True, stdout=subprocess.PIPE)
+    stdout, stderr = p.communicate()
+
+    if p.returncode:
+        return {
+            'flags': default_flags,
+            'do_cache': False,
+        }
+
+    flags = stdout.split(' ')
+    flags_relative = MakeRelativePathsInFlagsAbsolute(flags, os.path.join(DirectoryOfThisScript(), working_directory))
+    flags_final = [flag for flag in flags_relative if flag.startswith("-")]
+
+    return {
+        'flags': flags_final,
+        'do_cache': True,
+    }
+
+
+def FlagsForFile(filename, **kwargs):
+    if sys.platform.startswith('linux'):
+        return FlagsForFileLinux(filename)
+
+    return {
+        'flags': default_flags,
+        'do_cache': False,
+    }