SERVER-26473 Implement the git based decider

1 files changed, 69 insertions, 0 deletions

diff --git a/site_scons/site_tools/git_decider.py b/site_scons/site_tools/git_decider.py
new file mode 100644
index 00000000000..cd69de95085
--- /dev/null
+++ b/site_scons/site_tools/git_decider.py
@@ -0,0 +1,69 @@
+# Copyright 2016 MongoDB Inc.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+# http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+
+# If available, uses Git metadata to decide whether files are out of date.
+
+def generate(env, **kwargs):
+
+    # Grab the existing decider functions out of the environment
+    # so we can invoke them when we can't use Git.
+    base_decider = env.decide_target
+    if (base_decider != env.decide_source):
+        raise Exception("Decider environment seems broken")
+
+    from git import Git
+    thisRepo = Git(env.Dir('#').abspath)
+    currentGitState = thisRepo.ls_files('--stage')
+    lines = currentGitState.split('\n')
+
+    file_sha1_map = {}
+    for line in lines:
+        line_content = line.split()
+        file_sha1_map[env.File(line_content[3]).path] = line_content[1]
+
+    for m in thisRepo.ls_files('-m').split('\n'):
+        if (m):
+            del file_sha1_map[env.File(m).path]
+
+    def is_known_to_git(dependency):
+        return str(dependency) in file_sha1_map
+
+    def git_says_file_is_up_to_date(dependency, prev_ni):
+        gitInfoForDep = file_sha1_map[str(dependency)]
+
+        if prev_ni is None:
+            dependency.get_ninfo().csig = gitInfoForDep
+            return False
+
+        if not(hasattr(prev_ni, 'csig')):
+            prev_ni.csig = gitInfoForDep
+
+        result = gitInfoForDep == prev_ni.csig
+        return result
+
+    def MongoGitDecider(dependency, target, prev_ni):
+        if not is_known_to_git(dependency):
+            return base_decider(dependency, target, prev_ni)
+        return not git_says_file_is_up_to_date(dependency, prev_ni)
+
+    env.Decider(MongoGitDecider)
+
+def exists(env):
+    try:
+        from git import Git
+        Git(env.Dir('#').abspath).ls_files('--stage')
+        return True
+    except:
+        return False