narrow: fix commits of empty files
The problem is that when committing a new file with empty contents (or
in general empty file with filelog p1 = -1), hg commit with narrow
doesn't create a filelog revision at all, which causes failures in
further commands.
The problem seems to be that:
- hg thinks that instead of creating a new filelog revision, it can
use the filelog's p1 (the nullrev)
- because it thinks the file contents is the same in that revision and
in p1
- because `narrowfilelog.cmp(nullrev, b'')` is True (unlike with
`filelog.cmp`)
It's not clear to me which `cmp` behaves better. But I think it makes
sense to change the commit code to not to "reuse" the null rev when
adding an empty file with filelog p1 == filelog p2 == -1. This is
consistent with never writing the null rev in the manifest, which `hg
verify` claims is an invariant:
```
inside/c@4: manifest refers to unknown revision
000000000000
```
Differential Revision: https://phab.mercurial-scm.org/D11400
narrow: show repo corruption when commiting empty files
Differential Revision: https://phab.mercurial-scm.org/D11399
filemerge: be more strict when detecting conflict markers, add `|` markers
I received a user complaint about detecting a line that contained 78 `=`
followed by `*/` as a conflict marker. We'll never generate that, we generate 7
identical characters and either the end of the line, or a space. Let's be
explicit about detecting exactly what we produce to reduce the chances of a
false positive.
While we're here, add `|||||||` as a detected conflict marker (generated with
the `keep-merge3` style conflicts).
Differential Revision: https://phab.mercurial-scm.org/D11391