CONTRIBUTING: document how to describe issue fix in commit header
@@ -94,6 +94,8 @@ The format can be described more formally:
<BLANK LINE>
<why this change was made>
<BLANK LINE>
+<FIX LINE>
+<BLANK LINE>
<SOB LINE>
```
@@ -107,6 +109,8 @@ If the change affects many subsystems, you can use ```*``` instead, like ```*:``
The message of commit body should describe why the change was made and how the code works at the high level.
+`<FIX LINE>` is optional. Please write the issue number at `<FIX LINE>` when your commit fixes an issue on Inclavare Containers project. Once the commit is submitted, the issue of Inclavare Containers project will be automatically closed.
+
#### Sign your work
A DCO sign-off is a line placed at the end of a commit message containing a contributor's signature.
