tests: simplify test-rebase-transaction.t
The file was extracted from test-rebase-base.t in 8cef8f7d51d0
(test-rebase-base: clarify it is about the "--base" flag,
2017-10-05). This patch follows up that and clarifies the new file's
purpose and simplifies it a bit.
Differential Revision: https://phab.mercurial-scm.org/D2756
Mercurial
=========
Mercurial is a fast, easy to use, distributed revision control tool
for software developers.
Basic install::
$ make # see install targets
$ make install # do a system-wide install
$ hg debuginstall # sanity-check setup
$ hg # see help
Running without installing::
$ make local # build for inplace usage
$ ./hg --version # should show the latest version
See https://mercurial-scm.org/ for detailed installation
instructions, platform-specific notes, and Mercurial user information.