``install -C'' / unnecessarily updating time stamps

[Thomas Schwinge]

Hello!

Please tell me if that has been discussed before -- I couldn't come up
with good search terms to check myself.


Automake section.

I was thinking about the following: when in a package P1 (using Automake)
e.g. C header files are installed via ``make install'', they are
installed unconditionally.  This has the effect that in a package P2,
that `#include's such C header files, a lot of files will have to be
rebuilt each time P1's ``make install'' has been run.  Why not have P1's
build system (i.e. Automake) overwrite files on installation only if
their content actually changed?


Coreutils section.

E.g. FreeBSD's `install' program is described to offer the following
functionality, which is currently not supported by GNU coreutils's.

http://www.freebsd.org/cgi/man.cgi?query=install
#v+
[...]
     -C      Copy the file.  If the target file already exists and the files
             are the same, then do not change the modification time of the
             target.  If the target's file flags and mode need not to be
             changed, the target's inode change time is also unchanged.
[...]
#v-

I found the following patch,
<http://cvs.pld.org.pl/SOURCES/coreutils-install-C.patch?rev=1.4> to add
such functionality.  What about adding that or something equivalent?


Automake section.

What about enhancing the `install-sh' shell script to also provide this
functionality?  (I could add that.)


Autoconf section.

What about having Autoconf's `AC_PROG_INSTALL' automatically use this
functionality if available?


Regards,
 Thomas

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