When passing start_branch on committing from the WebIDE, it's possible
that the branch has changed since editing started, which results in the
change being applied on top of the latest commit in the branch and
overwriting the new changes.
By passing the start_sha instead we can make sure that the change is
applied on top of the commit which the user started editing from.
FFaker can generate data that randomly break our test suite. This
simplifies our factories and use sequences which are more predictive.
Signed-off-by: Rémy Coutable <remy@rymai.me>
