diff --stat: use less columns for change counts

Number of columns required for change counts is now computed based on
the maximum number of changed lines instead of being fixed. This means
that usually a few more columns will be available for the filenames
and the graph.

The graph width logic is also modified to include enough space for
"Bin XXX -> YYY bytes".

If changes to binary files are mixed with changes to text files,
change counts are padded to take at least three columns. And the other
way around, if change counts require more than three columns, then
"Bin"s are padded to align with the change count. This way, the +-
part starts in the same column as "XXX -> YYY" part for binary files.
This makes the graph easier to parse visually thanks to the empty
column. This mimics the layout of diff --stat before this change.

Tests and the tutorial are updated to reflect the new --stat output.
This means either the removal of extra padding and/or the addition of
up to three extra characters to truncated filenames. One test is added
to check the graph alignment when a binary file change and text file
change of more than 999 lines are committed together.

Signed-off-by: Zbigniew Jędrzejewski-Szmek <zbyszek@in.waw.pl>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
t/gitweb-lib: use $PERL_PATH to run gitweb

The current code runs "perl gitweb.cgi" to test gitweb. This
will use whatever version of perl happens to be first in the
PATH. We are better off using the specific perl that the
user specified via PERL_PATH, which matches what gets put on
the #!-line of the built gitweb.cgi.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
xdiff: choose XDL_FAST_HASH code on sizeof(long) instead of __WORDSIZE

Darwin does not define __WORDSIZE, and compiles the 32-bit code path
on 64-bit systems, resulting in a totally broken git.

I could not find an alternative -- other than the platform symbols
(__x86_64__ etc.) -- that does the test in the preprocessor.  However,
we can also just test for the size of a 'long', which is what really
matters here.  Any compiler worth its salt will leave only the branch
relevant for its platform, and indeed on Linux/GCC the numbers don't
change:

 Test                                  tr/darwin-xdl-fast-hash   origin/next              origin/master
 ------------------------------------------------------------------------------------------------------------------
 4000.1: log -3000 (baseline)          0.09(0.07+0.01)           0.09(0.07+0.01) -5.5%*   0.09(0.07+0.01) -4.1%
 4000.2: log --raw -3000 (tree-only)   0.47(0.41+0.05)           0.47(0.40+0.05) -0.5%    0.45(0.38+0.06) -3.5%.
 4000.3: log -p -3000 (Myers)          1.81(1.67+0.12)           1.81(1.67+0.13) +0.3%    1.99(1.84+0.12) +10.2%***
 4000.4: log -p -3000 --histogram      1.79(1.66+0.11)           1.80(1.67+0.11) +0.4%    1.96(1.82+0.10) +9.2%***
 4000.5: log -p -3000 --patience       2.17(2.02+0.13)           2.20(2.04+0.13) +1.3%.   2.33(2.18+0.13) +7.4%***
 ------------------------------------------------------------------------------------------------------------------
 Significance hints:  '.' 0.1  '*' 0.05  '**' 0.01  '***' 0.001

Noticed-by: Brian Gernhardt <brian@gernhardtsoftware.com>
Signed-off-by: Thomas Rast <trast@student.ethz.ch>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Consistently use perl from /usr/bin/ for scripts

While the majority of scripts use '#!/usr/bin/perl', some use
'#!/usr/bin/env perl'. In the end there is no difference, because the
Makefile rewrites "#!.*perl" with "#!$PERL_PATH" in scripted
Porcelains before installing. Nevertheless, the second form can be
misleading, because it suggests that perl found first in $PATH will be
used.

Suggested-by: Junio C Hamano <gitster@pobox.com>
Signed-off-by: Zbigniew Jędrzejewski-Szmek <zbyszek@in.waw.pl>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Merge branch 'tr/xdiff-fast-hash' into next

Use word-at-a-time comparison to find end of line or NUL (end of buffer),
borrowed from the linux-kernel discussion.

By Thomas Rast
* tr/xdiff-fast-hash:
  xdiff: choose XDL_FAST_HASH code on sizeof(long) instead of __WORDSIZE
Merge branch 'jk/maint-gitweb-test-use-sane-perl' into next

By Jeff King (1) and Zbigniew Jędrzejewski-Szmek (1)
* jk/maint-gitweb-test-use-sane-perl:
  Consistently use perl from /usr/bin/ for scripts
  t/gitweb-lib: use $PERL_PATH to run gitweb
Merge branch 'zj/diff-stat-smaller-num-columns' into next

Spend only minimum number of columns necessary to show the number of lines
in the output from "diff --stat", instead of always allocating 4 columns
even when showing changes that are much smaller than 1000 lines.

By Zbigniew Jędrzejewski-Szmek
* zj/diff-stat-smaller-num-columns:
  diff --stat: use less columns for change counts