misc: Updated CONTRIBUTING.md to discuss branches

There are some circumstances in which branches may be beneficial.
Though, in general, they should be discouraged. Therefore,
CONTRIBUTING.md has been enhanced to outline under what circumstances
creation of new branches is allowed and how they may be created and
used.

Change-Id: I2df8b38868e5c8146b068d9e7e957abbe3cf3b38
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/24263
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>
Reviewed-by: Matt Sinclair <mattdsinclair@gmail.com>
Reviewed-by: Giacomo Travaglini <giacomo.travaglini@arm.com>
Maintainer: Bobby R. Bruce <bbruce@ucdavis.edu>
Tested-by: kokoro <noreply+kokoro@google.com>

1 files changed, 32 insertions, 0 deletions

diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index d3b081b71..bd0eafbfe 100644
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -308,6 +308,38 @@ gerrit (e.g., reviewers, labels). The gerrit documentation has more
 information.
 https://gerrit-review.googlesource.com/Documentation/user-upload.html
 
+Branches
+========
+
+By default, contributions to gem5 should be made on the master branch. Branches
+are generally discouraged due to their tendency to bloat git repositories with
+abandoned code. However, the creation of branches is permitted for development
+of a specific feature or improvement if one or more of the following criteria
+are met:
+
+1. The feature/improvement is likely to be of a large size, consisting of many
+commits, with little logic in these commits being contributed separately.
+2. The feature/improvement will be developed over a long period of time.
+3. There is sufficient reason that a feature/improvement should not be merged
+into the master branch yet (e.g., the feature/improvement is not intended for
+the next release but a future release).
+
+If a branch is required it can only be created by a project maintainer.
+Therefore, if a gem5 contributor desires a separate branch for their work, they
+should request one from the maintainer of the component the work relates to
+(see MAINTAINERS for the list of maintainers and the components they are
+responsible for). **The maintainer shall use their discretion to determine
+whether the creation of a branch is necessary**. If approved, the maintainer
+shall create the branch which the contributor may then use.
+
+Development on a branch within Gerrit functions in exactly the same way as
+contributing to the master branch. When contributors to a branch are satisfied,
+they should create a merge commit into the master branch. The maintainer should
+then be notified that the branch they created can now be deleted.
+
+**Abandonment of changes within branches may result in these branches being
+removed from the repository. All branches within a repo should be under active
+development.**
 
 Reviewing patches
 =================