merge: print status message before launching external merge tool
It seems somewhat common that people run into a merge conflict and
don't notice the launched merge tool, and instead they think hg just
hung. Let's print a message for each file that we launch a GUI merge
tool for.
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.