Summary:
This commit doesn't change license of any file. It just makes the license implicit (inherited from LICENSE file in the root directory).
We are removing the headers for these reasons:
- It wastes space in editors, less code is visible in editor upon opening a file.
- It brings noise to diff of the first change of any file every year.
- It confuses Git file copy detection when creating small files.
- We don't have an explicit license header in other files (JS, CSS, images, documentation).
- Using license header in every file is not obligatory: http://www.apache.org/dev/apply-license.html#new.
This change is approved by Alma Chao (Lead Open Source and IP Counsel at Facebook).
Test Plan: Verified that the license survived only in LICENSE file and that it didn't modify externals.
Reviewers: epriestley, davidrecordon
Reviewed By: epriestley
CC: aran, Korvin
Maniphest Tasks: T2035
Differential Revision: https://secure.phabricator.com/D3886
Summary:
Certain types of things we should be storing in edges (notably, Task X depends on Task Y) should always be acyclic. Allow `PhabricatorEdgeEditor` to enforce this, since we can't correctly enforce it outside of the editor without being vulnerable to races.
Each edge type can be marked acyclic. If an edge type is acyclic, we perform additional steps when writing new edges of that type:
- We acquire a global lock on the edge type before performing any reads or writes. This ensures we can't produce a cycle as a result of a race where two edits add edges which independently do not produce a cycle, but do produce a cycle when combined.
- After performing writes but before committing transactions, we load the edge graph for each acyclic type and verify that it is, in fact, acyclic. If we detect cycles, we abort the edit.
- When we're done, we release the edge type locks.
This is a relatively high-complexity change, but gives us a simple way to flag an edge type as acyclic in a robust way.
Test Plan: Ran unit tests.
Reviewers: btrahan
Reviewed By: btrahan
CC: aran
Maniphest Tasks: T1162
Differential Revision: https://secure.phabricator.com/D2940
