pager: drop "wait for output to run less" hack

Commit 35ce862 (pager: Work around window resizing bug in
'less', 2007-01-24) causes git's pager sub-process to wait
to receive input after forking but before exec-ing the
pager. To handle this, run-command had to grow a "pre-exec
callback" feature. Unfortunately, this feature does not work
at all on Windows (where we do not fork), and interacts
poorly with run-command's parent notification system. Its
use should be discouraged.

The bug in less was fixed in version 406, which was released
in June 2007. It is probably safe at this point to remove
our workaround. That lets us rip out the preexec_cb feature
entirely.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
autoconf: GIT_CONF_APPEND_LINE: change signature

Change one-argument GIT_CONF_APPEND_LINE([VAR=VAL]) to
GIT_CONF_APPEND_LINE([VAR], [VAL]), that is more similar to the usual
AC_SUBST macro; this is only a preparatory change in view of future
refactorings.

No semantic change is intended.  In fact, the generated configure file
doesn't change at all.

Signed-off-by: Stefano Lattarini <stefano.lattarini@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
autoconf: GIT_CONF_APPEND_LINE -> GIT_CONF_SUBST

The new name fits better with the macro signature, and underlines the
similarities with the autoconf-provided macro AC_SUBST (which will be
made even more pronounced in planned future commits).

Once again, no semantic change is intended, and indeed no change to the
generated configure script is expected.

Signed-off-by: Stefano Lattarini <stefano.lattarini@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
autoconf: remove some redundant shell indirections

They are merely useless now, but would get in the way of future changes.

No semantic change is intended.

Signed-off-by: Stefano Lattarini <stefano.lattarini@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
autoconf: remove few redundant semicolons

They are merely useless now, but would get in the way of future changes.

No semantic change is intended.

Signed-off-by: Stefano Lattarini <stefano.lattarini@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
autoconf: use AC_CONFIG_COMMANDS instead of ad-hoc 'config.mak.append'

This will allow "./config.status --recheck; ./config.status" to work
correctly as a mean of reconfiguring the tree with the same configure
argument used in the previous "./configure" invocation.

Signed-off-by: Stefano Lattarini <stefano.lattarini@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
build: "make clean" should not remove configure-generated files

Those filed hold variables, settings and information set by the
configuration process run by './configure'; in Autotools-based
build system that kind of stuff should only be removed by
"make distclean".  Having it removed by "make clean" is not only
inconsistent, but causes real confusion for that part of the Git
audience that is used to the Autotools semantics; for example,
an autotools old-timer that has run:

    ./configure --prefix /opt/git

in the past, without running "make distclean" afterwards, would
expect a "make install" issued after a "make clean" to rebuild and
install git in '/opt/git'; but with the current behaviour, the
"make clean" invocation removes (among the other things) the file
'config.mak.autogen', so that the "make install" falls back to the
default prefix of '$HOME', thus installing git in the user's home
directory -- definitely unexpected.

Signed-off-by: Stefano Lattarini <stefano.lattarini@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
build: reconfigure automatically if configure.ac changes

This provides a reduced but still useful sibling of the Automake's
"automatic Makefile rebuild" feature.  It's important to note that
we take care to enable the new rules only if the tree that has already
be configured with './configure', so that users relying on manual
configuration won't be negatively impacted.

Signed-off-by: Stefano Lattarini <stefano.lattarini@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
difftool: only copy back files modified during directory diff

When 'difftool --dir-diff' is used to compare working tree files,
it always copies files from the tmp dir back to the working tree
when the diff tool is closed, even if the files were not modified
by the diff tool.

This causes the file timestamp to change. Files should only be
copied from the tmp dir back to the working copy if they were
actually modified.

Signed-off-by: Tim Henigan <tim.henigan@gmail.com>
Signed-off-by: David Aguilar <davvid@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
block-sha1: avoid pointer conversion that violates alignment constraints

With 660231aa (block-sha1: support for architectures with memory
alignment restrictions, 2009-08-12), blk_SHA1_Update was modified to
access 32-bit chunks of memory one byte at a time on arches that
prefer that:

	#define get_be32(p)    ( \
		(*((unsigned char *)(p) + 0) << 24) | \
		(*((unsigned char *)(p) + 1) << 16) | \
		(*((unsigned char *)(p) + 2) <<  8) | \
		(*((unsigned char *)(p) + 3) <<  0) )

The code previously accessed these values by just using htonl(*p).

Unfortunately, Michael noticed on an Alpha machine that git was using
plain 32-bit reads anyway.  As soon as we convert a pointer to int *,
the compiler can assume that the object pointed to is correctly
aligned as an int (C99 section 6.3.2.3 "pointer conversions"
paragraph 7), and gcc takes full advantage by using a single 32-bit
load, resulting in a whole bunch of unaligned access traps.

So we need to obey the alignment constraints even when only dealing
with pointers instead of actual values.  Do so by changing the type
of 'data' to void *.  This patch renames 'data' to 'block' at the same
time to make sure all references are updated to reflect the new type.

Reported-tested-and-explained-by: Michael Cree <mcree@orcon.net.nz>
Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
block-sha1: put expanded macro parameters in parentheses

't' is currently always a numeric constant, but it can't hurt to
prepare for the day that it becomes useful for a caller to pass in a
more complex expression.

Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Makefile: fix location of listing produced by "make subdir/foo.s"

When I invoke "make block-sha1/sha1.s", 'make' runs $(CC) -S without
specifying where it should put its output and the output ends up in
./sha1.s.  Confusing.

Add an -o option to the .s rule to fix this.  We were already doing
that for most compiler invocations but had forgotten it for the
assembler listings.

Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Makefile: BLK_SHA1 does not require fast htonl() and unaligned loads

block-sha1/ is fast on most known platforms.  Clarify the Makefile to
be less misleading about that.

Early versions of block-sha1/ explicitly relied on fast htonl() and
fast 32-bit loads with arbitrary alignment.  Now it uses those on some
arches but the default behavior is byte-at-a-time access for the sake
of arches like ARM, Alpha, and their kin and it is still pretty fast
on these arches (fast enough to supersede the mozilla SHA1
implementation and the hand-written ARM assembler implementation that
were bundled before).

Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Merge branch 'sl/autoconf' into next

* sl/autoconf:
  build: reconfigure automatically if configure.ac changes
  build: "make clean" should not remove configure-generated files
  autoconf: use AC_CONFIG_COMMANDS instead of ad-hoc 'config.mak.append'
  autoconf: remove few redundant semicolons
  autoconf: remove some redundant shell indirections
  autoconf: GIT_CONF_APPEND_LINE -> GIT_CONF_SUBST
  autoconf: GIT_CONF_APPEND_LINE: change signature
Merge branch 'th/difftool-diffall' into next

* th/difftool-diffall:
  difftool: only copy back files modified during directory diff
Merge branch 'jn/block-sha1' into next

* jn/block-sha1:
  Makefile: BLK_SHA1 does not require fast htonl() and unaligned loads
  block-sha1: put expanded macro parameters in parentheses
  block-sha1: avoid pointer conversion that violates alignment constraints
Merge branch 'jn/make-assembly-in-right-directory' into next

* jn/make-assembly-in-right-directory:
  Makefile: fix location of listing produced by "make subdir/foo.s"
Merge branch 'jk/no-more-pre-exec-callback' into next

Will defer for 6 months until ancient "less" goes extinct.

* jk/no-more-pre-exec-callback:
  pager: drop "wait for output to run less" hack