ui: allow open editor with custom filename
By default, editor will use temp file named after hard-coded pattern
'hg-editor-XXX.txt' which makes it impossible for extensions to use
another filename if desired.
Now the middle part of the pattern ('editor') can be changed by
setting extra['prefix'].
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.