tests/test-eolfilename.t

posix: always seek to EOF when opening a file in append mode

Python 3 already does this, so skip it there.

Consider the program:

   #include <stdio.h>

   int main() {
     FILE *f = fopen("narf", "w");
     fprintf(f, "narf\n");
     fclose(f);

     f = fopen("narf", "a");
     printf("%ld\n", ftell(f));
     fprintf(f, "troz\n");
     printf("%ld\n", ftell(f));

     return 0;
   }

on macOS, FreeBSD, and Linux with glibc, this program prints

   5
   10

but on musl libc (Alpine Linux and probably others) this prints

   0
   10

By my reading of
https://pubs.opengroup.org/onlinepubs/009695399/functions/fopen.html
this is technically correct, specifically:

> Opening a file with append mode (a as the first character in the
> mode argument) shall cause all subsequent writes to the file to be
> forced to the then current end-of-file, regardless of intervening
> calls to fseek().

in other words, the file position doesn't really matter in append-mode
files, and we can't depend on it being at all meaningful unless we
perform a seek() before tell() after open(..., 'a'). Experimentally
after a .write() we can do a .tell() and it'll always be reasonable,
but I'm unclear from reading the specification if that's a smart thing
to rely on. This matches what we do on Windows and what Python 3 does
for free, so let's just be consistent. Thanks to Yuya for the idea.

#require eol-in-paths

https://bz.mercurial-scm.org/352

test issue352

  $ hg init foo
  $ cd foo
  $ A=`printf 'he\rllo'`
  $ echo foo > "$A"
  $ hg add
  adding he\r (no-eol) (esc)
  llo
  abort: '\n' and '\r' disallowed in filenames: 'he\rllo'
  [255]
  $ hg ci -A -m m
  adding he\r (no-eol) (esc)
  llo
  abort: '\n' and '\r' disallowed in filenames: 'he\rllo'
  [255]
  $ rm "$A"
  $ echo foo > "hell
  > o"
  $ hg add
  adding hell
  o
  abort: '\n' and '\r' disallowed in filenames: 'hell\no'
  [255]
  $ hg ci -A -m m
  adding hell
  o
  abort: '\n' and '\r' disallowed in filenames: 'hell\no'
  [255]
  $ echo foo > "$A"
  $ hg debugwalk -v
  * matcher:
  <alwaysmatcher>
  f  he\r (no-eol) (esc)
  llo  he\r (no-eol) (esc)
  llo
  f  hell
  o  hell
  o

  $ echo bla > quickfox
  $ hg add quickfox
  $ hg ci -m 2
  $ A=`printf 'quick\rfox'`
  $ hg cp quickfox "$A"
  abort: '\n' and '\r' disallowed in filenames: 'quick\rfox'
  [255]
  $ hg mv quickfox "$A"
  abort: '\n' and '\r' disallowed in filenames: 'quick\rfox'
  [255]

https://bz.mercurial-scm.org/2036

  $ cd ..

test issue2039

  $ hg init bar
  $ cd bar
  $ cat <<EOF >> $HGRCPATH
  > [extensions]
  > color =
  > [color]
  > mode = ansi
  > EOF
  $ A=`printf 'foo\nbar'`
  $ B=`printf 'foo\nbar.baz'`
  $ touch "$A"
  $ touch "$B"
  $ hg status --color=always
  \x1b[0;35;1;4m? \x1b[0m\x1b[0;35;1;4mfoo\x1b[0m (esc)
  \x1b[0;35;1;4mbar\x1b[0m (esc)
  \x1b[0;35;1;4m? \x1b[0m\x1b[0;35;1;4mfoo\x1b[0m (esc)
  \x1b[0;35;1;4mbar.baz\x1b[0m (esc)

  $ cd ..