tests/test-issue619.t

filelog: don't crash on invalid copy metadata (issue5748)

"copy" and "copyrev" are both supposed to appear next to each other.
However, a user report demonstrated a crash that indicates that
something in the wild is producing "copy" without "copyrev"
(probably `hg convert`).

While we should definitely fix the source of the bad metadata,
the bad code causing the crash is already in the wild and who knows
how many repositories are impacted. So let's be more defensive
when accessing the file revision metadata.

https://bz.mercurial-scm.org/619

  $ hg init
  $ echo a > a
  $ hg ci -Ama
  adding a

  $ echo b > b
  $ hg branch b
  marked working directory as branch b
  (branches are permanent and global, did you want a bookmark?)
  $ hg ci -Amb
  adding b

  $ hg co -C 0
  0 files updated, 0 files merged, 1 files removed, 0 files unresolved

Fast-forward:

  $ hg merge b
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  (branch merge, don't forget to commit)
  $ hg ci -Ammerge

Bogus fast-forward should fail:

  $ hg merge b
  abort: merging with a working directory ancestor has no effect
  [255]

Even with strange revset (issue4465)

  $ hg merge ::.
  abort: merging with a working directory ancestor has no effect
  [255]