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 repobundlerepo
$ cat <<EOF >> $HGRCPATH
> [extensions]
> mq=
> [alias]
> tlog = log --template "{rev}: {node|short} {desc}\\n"
> theads = heads --template "{rev}: {desc}\\n"
> tincoming = incoming --template "{rev}: {desc}\\n"
> EOF
Setup main:
$ hg init base
$ cd base
$ echo "One" > one
$ hg add
adding one
$ hg ci -m "main: one added"
$ echo "++" >> one
$ hg ci -m "main: one updated"
Bundle main:
$ hg bundle --base=null ../main.hg
2 changesets found
$ cd ..
Incoming to fresh repo:
$ hg init fresh
$ hg -R fresh tincoming main.hg
comparing with main.hg
0: main: one added
1: main: one updated
$ test -f ./fresh/.hg/hg-bundle* && echo 'temp. bundle file remained' || true
$ hg -R fresh tincoming bundle:fresh+main.hg
comparing with bundle:fresh+main.hg
0: main: one added
1: main: one updated
Setup queue:
$ cd base
$ hg qinit -c
$ hg qnew -m "patch: two added" two.patch
$ echo two > two
$ hg add
adding two
$ hg qrefresh
$ hg qcommit -m "queue: two.patch added"
$ hg qpop -a
popping two.patch
patch queue now empty
Bundle queue:
$ hg -R .hg/patches bundle --base=null ../queue.hgq
1 changesets found
$ test -f ./fresh/.hg/hg-bundle* && echo 'temp. bundle file remained' || true
$ cd ..
Clone base:
$ hg clone base copy
updating to branch default
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ cd copy
$ hg qinit -c
Incoming queue bundle:
$ hg -R .hg/patches tincoming ../queue.hgq
comparing with ../queue.hgq
0: queue: two.patch added
$ test -f .hg/hg-bundle* && echo 'temp. bundle file remained' || true
Pull queue bundle:
$ hg -R .hg/patches pull --update ../queue.hgq
pulling from ../queue.hgq
requesting all changes
adding changesets
adding manifests
adding file changes
added 1 changesets with 3 changes to 3 files
new changesets d7553909353d (1 drafts)
merging series
2 files updated, 1 files merged, 0 files removed, 0 files unresolved
$ test -f .hg/patches/hg-bundle* && echo 'temp. bundle file remained' || true
$ hg -R .hg/patches theads
0: queue: two.patch added
$ hg -R .hg/patches tlog
0: d7553909353d queue: two.patch added
$ hg qseries
two.patch
$ cd ..
Clone base again:
$ hg clone base copy2
updating to branch default
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ cd copy2
$ hg qinit -c
Unbundle queue bundle:
$ hg -R .hg/patches unbundle --update ../queue.hgq
adding changesets
adding manifests
adding file changes
added 1 changesets with 3 changes to 3 files
new changesets d7553909353d (1 drafts)
merging series
2 files updated, 1 files merged, 0 files removed, 0 files unresolved
$ hg -R .hg/patches theads
0: queue: two.patch added
$ hg -R .hg/patches tlog
0: d7553909353d queue: two.patch added
$ hg qseries
two.patch
$ cd ..