tests/test-issue1877.t

convert: correctly convert paths to UTF-8 for Subversion

The previous code using encoding.tolocal() only worked by chance in these
situations:

* The string is ASCII: The fast path was triggered and the string was returned
  unmodified.
* The local encoding is UTF-8: The source and target encoding is the same.
* The string is not valid UTF-8 and the native encoding is ISO-8859-1: If the
  string doesn’t decode using UTF-8, ISO-8859-1 is tried as a fallback. During
  `hg convert`, the local encoding is always UTF-8. The irony is that in this
  case, encoding.tolocal() behaves like what someone would expect the reverse
  function, encoding.fromlocal(), to do.

When the locale encoding is ISO-8859-15, trying to convert a SVN repo `/tmp/a€`
failed before like this:

file:///tmp/a%C2%A4 does not look like a Subversion repository to libsvn version 1.14.0

The correct URL is `file:///tmp/a%E2%82%AC`.

Unlike previously (with the ISO-8859-1 fallback), decoding the path using the
locale encoding can fail. In this case, we have to bail out, as Subversion
won’t be able to do anything useful with the path.

https://bz.mercurial-scm.org/1877

  $ hg init a
  $ cd a
  $ echo a > a
  $ hg add a
  $ hg ci -m 'a'
  $ echo b > a
  $ hg ci -m'b'
  $ hg up 0
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ hg book main
  $ hg book
   * main                      0:cb9a9f314b8b
  $ echo c > c
  $ hg add c
  $ hg ci -m'c'
  created new head
  $ hg book
   * main                      2:d36c0562f908
  $ hg heads
  changeset:   2:d36c0562f908
  bookmark:    main
  tag:         tip
  parent:      0:cb9a9f314b8b
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     c
  
  changeset:   1:1e6c11564562
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     b
  
  $ hg up 1e6c11564562
  1 files updated, 0 files merged, 1 files removed, 0 files unresolved
  (leaving bookmark main)
  $ hg merge main
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  (branch merge, don't forget to commit)
  $ hg book
     main                      2:d36c0562f908
  $ hg ci -m'merge'
  $ hg book
     main                      2:d36c0562f908

  $ cd ..