simplemerge: make minimize() a free function
IMO, `Merge3Text` should be about merging text without knowing about
conflict markers. "Conflict minimization" is about making conflict
markers smaller, so it should be moved out. This patch does that. I'll
refactor it next.
Differential Revision: https://phab.mercurial-scm.org/D11980
$ rm -rf a
$ hg init a
$ cd a
$ echo a > a
$ hg ci -Am0
adding a
$ hg tag t1 # 1
$ hg tag --remove t1 # 2
$ hg co 1
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ hg tag -f -r0 t1
$ hg tags
tip 3:a49829c4fc11
t1 0:f7b1eb17ad24
$ cd ..