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.
$ unset HGUSER
$ EMAIL="My Name <myname@example.com>"
$ export EMAIL
$ hg init test
$ cd test
$ touch asdf
$ hg add asdf
$ hg commit -m commit-1
$ hg tip
changeset: 0:53f268a58230
tag: tip
user: My Name <myname@example.com>
date: Thu Jan 01 00:00:00 1970 +0000
summary: commit-1
$ unset EMAIL
$ echo 1234 > asdf
$ hg commit -u "foo@bar.com" -m commit-1
$ hg tip
changeset: 1:3871b2a9e9bf
tag: tip
user: foo@bar.com
date: Thu Jan 01 00:00:00 1970 +0000
summary: commit-1
$ echo "[ui]" >> .hg/hgrc
$ echo "username = foobar <foo@bar.com>" >> .hg/hgrc
$ echo 12 > asdf
$ hg commit -m commit-1
$ hg tip
changeset: 2:8eeac6695c1c
tag: tip
user: foobar <foo@bar.com>
date: Thu Jan 01 00:00:00 1970 +0000
summary: commit-1
$ echo 1 > asdf
$ hg commit -u "foo@bar.com" -m commit-1
$ hg tip
changeset: 3:957606a725e4
tag: tip
user: foo@bar.com
date: Thu Jan 01 00:00:00 1970 +0000
summary: commit-1
$ echo 123 > asdf
$ echo "[ui]" > .hg/hgrc
$ echo "username = " >> .hg/hgrc
$ hg commit -m commit-1
abort: no username supplied
(use 'hg config --edit' to set your username)
[255]
# test alternate config var
$ echo 1234 > asdf
$ echo "[ui]" > .hg/hgrc
$ echo "user = Foo Bar II <foo2@bar.com>" >> .hg/hgrc
$ hg commit -m commit-1
$ hg tip
changeset: 4:6f24bfb4c617
tag: tip
user: Foo Bar II <foo2@bar.com>
date: Thu Jan 01 00:00:00 1970 +0000
summary: commit-1
# test prompt username
$ cat > .hg/hgrc <<EOF
> [ui]
> askusername = True
> EOF
$ echo 12345 > asdf
$ hg commit --config ui.interactive=False -m ask
enter a commit username:
no username found, using '[^']*' instead (re)
$ hg rollback -q
$ hg commit --config ui.interactive=True -m ask <<EOF
> Asked User <ask@example.com>
> EOF
enter a commit username: Asked User <ask@example.com>
$ hg tip
changeset: 5:84c91d963b70
tag: tip
user: Asked User <ask@example.com>
date: Thu Jan 01 00:00:00 1970 +0000
summary: ask
# test no .hg/hgrc (uses generated non-interactive username)
$ echo space > asdf
$ rm .hg/hgrc
$ hg commit -m commit-1 2>&1
no username found, using '[^']*' instead (re)
$ echo space2 > asdf
$ hg commit -u ' ' -m commit-1
transaction abort!
rollback completed
abort: empty username!
[255]
# don't add tests here, previous test is unstable
$ cd ..