Signed-off-by: NJunio C Hamano <junkio@cox.net>

This patch makes the usage(), die() and error() handlers customizable.
Nothing in the git code itself uses that but many other libgit users
(like Git.pm) will.

This is implemented using the mutator functions primarily because you
cannot directly modifying global variables of libgit from a program that
dlopen()ed it, apparently. But having functions for that is a better API
anyway.
Signed-off-by: NPetr Baudis <pasky@suse.cz>
Signed-off-by: NJunio C Hamano <junkio@cox.net>

This attempts to clean up the way various compatibility
functions are defined and used.

 - A new header file, git-compat-util.h, is introduced.  This
   looks at various NO_XXX and does necessary function name
   replacements, equivalent of -Dstrcasestr=gitstrcasestr in the
   Makefile.

 - Those function name replacements are removed from the Makefile.

 - Common features such as usage(), die(), xmalloc() are moved
   from cache.h to git-compat-util.h; cache.h includes
   git-compat-util.h itself.
Signed-off-by: NJunio C Hamano <junkio@cox.net>

Instead of "git status" ignoring (and hiding) potential errors from the
"git-update-index" call, make it exit if it fails, and show the error.

In order to do this, use the "-q" flag (to ignore not-up-to-date files)
and add a new "--unmerged" flag that allows unmerged entries in the index
without any errors.

This also avoids marking the index "changed" if an entry isn't actually
modified, and makes sure that we exit with an understandable error message
if the index is corrupt or unreadable. "read_cache()" no longer returns an
error for the caller to check.

Finally, make die() and usage() exit with recognizable error codes, if we
ever want to check the failure reason in scripts.
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>
Signed-off-by: NJunio C Hamano <junkio@cox.net>

Add <limits.h> to the include files handled by "cache.h", and remove
extraneous #include directives from various .c files. The rule is that
"cache.h" gets all the basic stuff, so that we'll have as few system
dependencies as possible.

Do the usage and error reporting in "usage.c", and the sha1 file
accesses in "sha1_file.c".

Small, nice, easily separated parts. Good.