tests/test-merge6.t

filemerge: introduce class whose objects represent files not in a context

Most code is going to barf at the return values here (particularly from data
and size), so we restrict it to the filemerge code.

This is already somewhat supported via:

  ctx.filectx(f, fileid=nullid)

Indeed, for add/add conflicts (ancestor doesn't have the file) we use precisely
that. However, that is broken in subtle ways:
- The cmp() function in filectx returns False (identical) for such a filectx
  when compared to a zero-length file.
- size() returns 0 rather than some sort of value indicating that the file isn't
  present.
- data() returns '' rather than some sort of value indicating that the file isn't
  present.

Given the relatively niche use of such filectxes, this seems to be the simplest
way to fix all these issues.

  $ cat <<EOF > merge
  > import sys, os
  > print "merging for", os.path.basename(sys.argv[1])
  > EOF
  $ HGMERGE="python ../merge"; export HGMERGE

  $ hg init A1
  $ cd A1
  $ echo This is file foo1 > foo
  $ echo This is file bar1 > bar
  $ hg add foo bar
  $ hg commit -m "commit text"

  $ cd ..
  $ hg clone A1 B1
  updating to branch default
  2 files updated, 0 files merged, 0 files removed, 0 files unresolved

  $ cd A1
  $ rm bar
  $ hg remove bar
  $ hg commit -m "commit test"

  $ cd ../B1
  $ echo This is file foo22 > foo
  $ hg commit -m "commit test"

  $ cd ..
  $ hg clone A1 A2
  updating to branch default
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ hg clone B1 B2
  updating to branch default
  2 files updated, 0 files merged, 0 files removed, 0 files unresolved

  $ cd A1
  $ hg pull ../B1
  pulling from ../B1
  searching for changes
  adding changesets
  adding manifests
  adding file changes
  added 1 changesets with 1 changes to 1 files (+1 heads)
  (run 'hg heads' to see heads, 'hg merge' to merge)
  $ hg merge
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  (branch merge, don't forget to commit)
  $ hg commit -m "commit test"
bar should remain deleted.
  $ hg manifest --debug
  f9b0e817f6a48de3564c6b2957687c5e7297c5a0 644   foo

  $ cd ../B2
  $ hg pull ../A2
  pulling from ../A2
  searching for changes
  adding changesets
  adding manifests
  adding file changes
  added 1 changesets with 0 changes to 0 files (+1 heads)
  (run 'hg heads' to see heads, 'hg merge' to merge)
  $ hg merge
  0 files updated, 0 files merged, 1 files removed, 0 files unresolved
  (branch merge, don't forget to commit)
  $ hg commit -m "commit test"
bar should remain deleted.
  $ hg manifest --debug
  f9b0e817f6a48de3564c6b2957687c5e7297c5a0 644   foo

  $ cd ..