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.
$ cat >> $HGRCPATH <<EOF
> [extensions]
> convert=
> EOF
$ hg init t
$ cd t
$ echo a >> a
$ hg ci -Am a0 -d '1 0'
adding a
$ hg branch brancha
marked working directory as branch brancha
(branches are permanent and global, did you want a bookmark?)
$ echo a >> a
$ hg ci -m a1 -d '2 0'
$ echo a >> a
$ hg ci -m a2 -d '3 0'
$ echo a >> a
$ hg ci -m a3 -d '4 0'
$ hg up -C 0
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ hg branch branchb
marked working directory as branch branchb
$ echo b >> b
$ hg ci -Am b0 -d '6 0'
adding b
$ hg up -C brancha
1 files updated, 0 files merged, 1 files removed, 0 files unresolved
$ echo a >> a
$ hg ci -m a4 -d '5 0'
$ echo a >> a
$ hg ci -m a5 -d '7 0'
$ echo a >> a
$ hg ci -m a6 -d '8 0'
$ hg up -C branchb
2 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ echo b >> b
$ hg ci -m b1 -d '9 0'
$ hg up -C 0
0 files updated, 0 files merged, 1 files removed, 0 files unresolved
$ echo c >> c
$ hg branch branchc
marked working directory as branch branchc
$ hg ci -Am c0 -d '10 0'
adding c
$ hg up -C brancha
1 files updated, 0 files merged, 1 files removed, 0 files unresolved
$ hg ci --close-branch -m a7x -d '11 0'
$ hg up -C branchb
2 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ hg ci --close-branch -m b2x -d '12 0'
$ hg up -C branchc
1 files updated, 0 files merged, 1 files removed, 0 files unresolved
$ hg merge branchb
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
(branch merge, don't forget to commit)
$ hg ci -m c1 -d '13 0'
$ cd ..
convert with datesort
$ hg convert --datesort t t-datesort
initializing destination t-datesort repository
scanning source...
sorting...
converting...
12 a0
11 a1
10 a2
9 a3
8 a4
7 b0
6 a5
5 a6
4 b1
3 c0
2 a7x
1 b2x
0 c1
graph converted repo
$ hg -R t-datesort log -G --template '{rev} "{desc}"\n'
o 12 "c1"
|\
| _ 11 "b2x"
| |
| | _ 10 "a7x"
| | |
o | | 9 "c0"
| | |
| o | 8 "b1"
| | |
| | o 7 "a6"
| | |
| | o 6 "a5"
| | |
| o | 5 "b0"
|/ /
| o 4 "a4"
| |
| o 3 "a3"
| |
| o 2 "a2"
| |
| o 1 "a1"
|/
o 0 "a0"
convert with datesort (default mode)
$ hg convert t t-sourcesort
initializing destination t-sourcesort repository
scanning source...
sorting...
converting...
12 a0
11 a1
10 a2
9 a3
8 b0
7 a4
6 a5
5 a6
4 b1
3 c0
2 a7x
1 b2x
0 c1
graph converted repo
$ hg -R t-sourcesort log -G --template '{rev} "{desc}"\n'
o 12 "c1"
|\
| _ 11 "b2x"
| |
| | _ 10 "a7x"
| | |
o | | 9 "c0"
| | |
| o | 8 "b1"
| | |
| | o 7 "a6"
| | |
| | o 6 "a5"
| | |
| | o 5 "a4"
| | |
| o | 4 "b0"
|/ /
| o 3 "a3"
| |
| o 2 "a2"
| |
| o 1 "a1"
|/
o 0 "a0"
convert with closesort
$ hg convert --closesort t t-closesort
initializing destination t-closesort repository
scanning source...
sorting...
converting...
12 a0
11 a1
10 a2
9 a3
8 b0
7 a4
6 a5
5 a6
4 a7x
3 b1
2 b2x
1 c0
0 c1
graph converted repo
$ hg -R t-closesort log -G --template '{rev} "{desc}"\n'
o 12 "c1"
|\
| o 11 "c0"
| |
_ | 10 "b2x"
| |
o | 9 "b1"
| |
| | _ 8 "a7x"
| | |
| | o 7 "a6"
| | |
| | o 6 "a5"
| | |
| | o 5 "a4"
| | |
o | | 4 "b0"
|/ /
| o 3 "a3"
| |
| o 2 "a2"
| |
| o 1 "a1"
|/
o 0 "a0"