simplemerge: change _minimize() to minimize a single conflict...
simplemerge: change _minimize() to minimize a single conflict
`_minimize()` is weird in that it changes `a_lines` and `b_lines` but
leaves `base_lines` unchanged, which means they'll be
inconsistent. That was fine because the caller never used
`base_lines`. With the recent refactorings of this code, we can now
make this function cleaner by having it minimize a single conflict and
not care about `base_lines`.
This also makes the code simpler and makes the code for each
`render_*()` function more similar.
Differential Revision:
https://phab.mercurial-scm.org/D11981
