tests/test-update-names.t

ui: add special-purpose atexit functionality

In spite of its longstanding use, Python's built-in atexit code is
not suitable for Mercurial's purposes, for several reasons:

* Handlers run after application code has finished.

* Because of this, the code that runs handlers swallows exceptions
  (since there's no possible stacktrace to associate errors with).
  If we're lucky, we'll get something spat out to stderr (if stderr
  still works), which of course isn't any use in a big deployment
  where it's important that exceptions get logged and aggregated.

* Mercurial's current atexit handlers make unfortunate assumptions
  about process state (specifically stdio) that, coupled with the
  above problems, make it impossible to deal with certain categories
  of error (try "hg status > /dev/full" on a Linux box).

* In Python 3, the atexit implementation is completely hidden, so
  we can't hijack the platform's atexit code to run handlers at a
  time of our choosing.

As a result, here's a perfectly cromulent atexit-like implementation
over which we have control.  This lets us decide exactly when the
handlers run (after each request has completed), and control what
the process state is when that occurs (and afterwards).

Test update logic when there are renames or weird same-name cases between dirs
and files

Update with local changes across a file rename

  $ hg init r1 && cd r1

  $ echo a > a
  $ hg add a
  $ hg ci -m a

  $ hg mv a b
  $ hg ci -m rename

  $ echo b > b
  $ hg ci -m change

  $ hg up -q 0

  $ echo c > a

  $ hg up
  merging a and b to b
  warning: conflicts while merging b! (edit, then use 'hg resolve --mark')
  0 files updated, 0 files merged, 0 files removed, 1 files unresolved
  use 'hg resolve' to retry unresolved file merges
  [1]

Test update when local untracked directory exists with the same name as a
tracked file in a commit we are updating to
  $ hg init r2 && cd r2
  $ echo root > root && hg ci -Am root  # rev 0
  adding root
  $ echo text > name && hg ci -Am "name is a file"  # rev 1
  adding name
  $ hg up 0
  0 files updated, 0 files merged, 1 files removed, 0 files unresolved
  $ mkdir name
  $ hg up 1
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved

Test update when local untracked directory exists with some files in it and has
the same name a tracked file in a commit we are updating to. In future this
should be updated to give an friendlier error message, but now we should just
make sure that this does not erase untracked data
  $ hg up 0
  0 files updated, 0 files merged, 1 files removed, 0 files unresolved
  $ mkdir name
  $ echo text > name/file
  $ hg st
  ? name/file
  $ hg up 1
  abort: *: '$TESTTMP/r1/r2/name' (glob)
  [255]
  $ cd ..

#if symlink

Test update when two commits have symlinks that point to different folders
  $ hg init r3 && cd r3
  $ echo root > root && hg ci -Am root
  adding root
  $ mkdir folder1 && mkdir folder2
  $ ln -s folder1 folder
  $ hg ci -Am "symlink to folder1"
  adding folder
  $ rm folder
  $ ln -s folder2 folder
  $ hg ci -Am "symlink to folder2"
  $ hg up 1
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ cd ..

#endif

#if rmcwd

Test that warning is printed if cwd is deleted during update
  $ hg init r4 && cd r4
  $ mkdir dir
  $ cd dir
  $ echo a > a
  $ echo b > b
  $ hg add a b
  $ hg ci -m "file and dir"
  $ hg up -q null
  current directory was removed
  (consider changing to repo root: $TESTTMP/r1/r4)

#endif