filemerge: split internal merge into api entry point and internal helper
This is a step toward adding 'union merge' to the internal merge tool.
'union merge' is a merge strategy which adds both left and right hand side
of a conflict region. Git implements this merge strategy which is very
practical to have for merging to e.g. the Changelog file.
$ hg init
$ touch a
$ hg add a
$ hg commit -m "Added a"
$ touch main
$ hg add main
$ hg commit -m "Added main"
$ hg checkout 0
0 files updated, 0 files merged, 1 files removed, 0 files unresolved
'main' should be gone:
$ ls
a
$ touch side1
$ hg add side1
$ hg commit -m "Added side1"
created new head
$ touch side2
$ hg add side2
$ hg commit -m "Added side2"
$ hg log
changeset: 3:91ebc10ed028
tag: tip
user: test
date: Thu Jan 01 00:00:00 1970 +0000
summary: Added side2
changeset: 2:b932d7dbb1e1
parent: 0:c2eda428b523
user: test
date: Thu Jan 01 00:00:00 1970 +0000
summary: Added side1
changeset: 1:71a760306caf
user: test
date: Thu Jan 01 00:00:00 1970 +0000
summary: Added main
changeset: 0:c2eda428b523
user: test
date: Thu Jan 01 00:00:00 1970 +0000
summary: Added a
$ hg heads
changeset: 3:91ebc10ed028
tag: tip
user: test
date: Thu Jan 01 00:00:00 1970 +0000
summary: Added side2
changeset: 1:71a760306caf
user: test
date: Thu Jan 01 00:00:00 1970 +0000
summary: Added main
$ ls
a
side1
side2
$ hg update --debug -C 1
resolving manifests
branchmerge: False, force: True, partial: False
ancestor: 91ebc10ed028+, local: 91ebc10ed028+, remote: 71a760306caf
side1: other deleted -> r
removing side1
side2: other deleted -> r
removing side2
main: remote created -> g
getting main
1 files updated, 0 files merged, 2 files removed, 0 files unresolved
$ ls
a
main