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.
Path conflict checking is currently disabled by default because of issue5716.
Turn it on for this test.
$ cat >> $HGRCPATH << EOF
> [experimental]
> merge.checkpathconflicts=True
> EOF
$ hg init repo
$ cd repo
$ echo base > base
$ hg add base
$ hg commit -m "base"
$ hg bookmark -i base
$ echo 1 > a
$ hg add a
$ hg commit -m "file"
$ hg bookmark -i file
$ echo 2 > a
$ hg commit -m "file2"
$ hg bookmark -i file2
$ hg up -q 0
$ mkdir a
$ echo 2 > a/b
$ hg add a/b
$ hg commit -m "dir"
created new head
$ hg bookmark -i dir
Basic merge - local file conflicts with remote directory
$ hg up -q file
$ hg bookmark -i
$ hg merge --verbose dir
resolving manifests
a: path conflict - a file or link has the same name as a directory
the local file has been renamed to a~853701544ac3
resolve manually then use 'hg resolve --mark a'
moving a to a~853701544ac3
getting a/b
1 files updated, 0 files merged, 0 files removed, 1 files unresolved
use 'hg resolve' to retry unresolved file merges or 'hg merge --abort' to abandon
[1]
$ hg update --clean .
1 files updated, 0 files merged, 1 files removed, 0 files unresolved
$ rm a~853701544ac3
Basic update - local directory conflicts with remote file
$ hg up -q 0
$ mkdir a
$ echo 3 > a/b
$ hg up file
a: untracked directory conflicts with file
abort: untracked files in working directory differ from files in requested revision
[255]
$ hg up --clean file
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
(activating bookmark file)
Repo state is ok
$ hg sum
parent: 1:853701544ac3
file
branch: default
bookmarks: *file
commit: (clean)
update: 2 new changesets (update)
phases: 4 draft
Basic update - untracked file conflicts with remote directory
$ hg up -q 0
$ echo untracked > a
$ hg up --config merge.checkunknown=warn dir
a: replacing untracked file
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
(activating bookmark dir)
$ cat a.orig
untracked
$ rm -f a.orig
Basic clean update - local directory conflicts with changed remote file
$ hg up -q file
$ rm a
$ mkdir a
$ echo 4 > a/b
$ hg up file2
abort: *: *$TESTTMP/repo/a* (glob)
[255]
$ hg up --clean file2
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
(activating bookmark file2)
Repo state is ok
$ hg sum
parent: 2:f64e09fac717
file2
branch: default
bookmarks: *file2
commit: (clean)
update: 1 new changesets, 2 branch heads (merge)
phases: 4 draft