abspath: convert real_path_internal() to strbuf

Use strbuf instead of fixed-sized buffers in real_path() in order to
avoid the size limitations of the latter.

Signed-off-by: Rene Scharfe <l.s.r@web.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
wrapper: add xgetcwd()

Add the helper function xgetcwd(), which returns the current directory
or dies.  The returned string has to be free()d after use.

Helped-by: Duy Nguyen <pclouds@gmail.com>
Signed-off-by: Rene Scharfe <l.s.r@web.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
use xgetcwd() to get the current directory or die

Convert several calls of getcwd() and die() to use xgetcwd() instead.
This way we get rid of fixed-size buffers (which can be too small
depending on the used file system) and gain consistent error messages.

Signed-off-by: Rene Scharfe <l.s.r@web.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
use xgetcwd() to set $GIT_DIR

Instead of dying of a segmentation fault if getcwd() returns NULL, use
xgetcwd() to make sure to write a useful error message and then exit
in an orderly fashion.

Suggested-by: Jeff King <peff@peff.net>
Signed-off-by: Rene Scharfe <l.s.r@web.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
abspath: convert absolute_path() to strbuf

Move most of the code of absolute_path() into the new function
strbuf_add_absolute_path() and in the process transform it to use
struct strbuf and xgetcwd() instead of a PATH_MAX-sized buffer,
which can be too small on some file systems.

Signed-off-by: Rene Scharfe <l.s.r@web.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
use strbuf_add_absolute_path() to add absolute paths

Signed-off-by: Rene Scharfe <l.s.r@web.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>