To apply a suggested fix, we manually compute the Git tree which
results from applying the described modifications to the patch set.
That Git tree is transformed into a change edit if none exists or
merged with an existing one.
Similar to change edits, fixes may only be applied for the current
patch set if no change edit exists. If one exists, fixes may only be
applied for the patch set on which the change edit is based on.
To fail as early as possible, we now reject suggested fixes which
include overlapping replacements when they are provided as review input.
Change-Id: Iabf0d0af025b0878e839956d16f29693b1e74eee
30d6c7d3da