view tests/test-clone-update-order.t @ 42562:97ada9b8d51b stable 5.0.2

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.

  $ hg init
  $ echo foo > bar
  $ hg commit -Am default
  adding bar
  $ hg up -r null
  0 files updated, 0 files merged, 1 files removed, 0 files unresolved
  $ hg branch mine
  marked working directory as branch mine
  (branches are permanent and global, did you want a bookmark?)
  $ echo hello > world
  $ hg commit -Am hello
  adding world
  $ hg up -r null
  0 files updated, 0 files merged, 1 files removed, 0 files unresolved
  $ hg branch other
  marked working directory as branch other
  $ echo good > bye
  $ hg commit -Am other
  adding bye
  $ hg up -r mine
  1 files updated, 0 files merged, 1 files removed, 0 files unresolved

  $ hg clone -U -u . .#other ../b -r 0 -r 1 -r 2 -b other
  abort: cannot specify both --noupdate and --updaterev
  [255]

  $ hg clone -U .#other ../b -r 0 -r 1 -r 2 -b other
  adding changesets
  adding manifests
  adding file changes
  added 3 changesets with 3 changes to 3 files (+2 heads)
  new changesets 8c68ee086fd0:fcc393352796
  $ rm -rf ../b

  $ hg clone -u . .#other ../b -r 0 -r 1 -r 2 -b other
  adding changesets
  adding manifests
  adding file changes
  added 3 changesets with 3 changes to 3 files (+2 heads)
  new changesets 8c68ee086fd0:fcc393352796
  updating to branch mine
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ rm -rf ../b

  $ hg clone -u 0 .#other ../b -r 0 -r 1 -r 2 -b other
  adding changesets
  adding manifests
  adding file changes
  added 3 changesets with 3 changes to 3 files (+2 heads)
  new changesets 8c68ee086fd0:fcc393352796
  updating to branch default
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ rm -rf ../b

  $ hg clone -u 1 .#other ../b -r 0 -r 1 -r 2 -b other
  adding changesets
  adding manifests
  adding file changes
  added 3 changesets with 3 changes to 3 files (+2 heads)
  new changesets 8c68ee086fd0:fcc393352796
  updating to branch mine
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ rm -rf ../b

  $ hg clone -u 2 .#other ../b -r 0 -r 1 -r 2 -b other
  adding changesets
  adding manifests
  adding file changes
  added 3 changesets with 3 changes to 3 files (+2 heads)
  new changesets 8c68ee086fd0:fcc393352796
  updating to branch other
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ rm -rf ../b

Test -r mine ... mine is ignored:

  $ hg clone -u 2 .#other ../b -r mine -r 0 -r 1 -r 2 -b other
  adding changesets
  adding manifests
  adding file changes
  added 3 changesets with 3 changes to 3 files (+2 heads)
  new changesets 8c68ee086fd0:fcc393352796
  updating to branch other
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ rm -rf ../b

  $ hg clone .#other ../b -b default -b mine
  adding changesets
  adding manifests
  adding file changes
  added 3 changesets with 3 changes to 3 files (+2 heads)
  new changesets 8c68ee086fd0:fcc393352796
  updating to branch default
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ rm -rf ../b

  $ hg clone .#other ../b
  adding changesets
  adding manifests
  adding file changes
  added 1 changesets with 1 changes to 1 files
  new changesets fcc393352796
  updating to branch other
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ rm -rf ../b

  $ hg clone -U . ../c -r 1 -r 2 > /dev/null
  $ hg clone ../c ../b
  updating to branch other
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ rm -rf ../b ../c