Re: Git help for kernel archeology, suppress diffs caused by CVS keyword expansion

Hi,

On Mon, 23 Jul 2007, Jon Smirl wrote:

Thanks for working on this. I'd like to see it added to git toolkit. 

I plan to submit it to patchutils instead, since this is not really 
dependent on git.

This diff is way easier to read now. I can see that it has SPI support 
backported from some future version.

But... it still has some problems. For the phytec patch it's not getting 
the $Log changes in the qlogic files right.

You are correct.  This slipped by my eyes.

I'm checking the output diff line by line for problems. It's down to
11,528 lines from 88,787. That's a lot of junk removed, I'll have to
make sure it isn't removing too much.

May I ask you to test this version?

Thanks,
Dscho

-- snipsnap --
#!/usr/bin/perl

# This is a simple state machine.
#
# There is the state of the current file; its header is stored
# in $current_file to avoid outputting it when all hunks were
# culled.  It is only printed before the first hunk, and then
# set to "" to avoid outputting it twice.
#
# There are the states of the current hunk, stored in
# * $current_hunk (possibly modified hunk)
# * $start_minus, $start_plus (from the original)
# * $plus, $minus, $space (the current count of the respective lines)
# a hunk is only printed (in flush_hunk) if any '+' or '-' lines
# are left after filtering.
#
# For $Log..$, there is the state $skip_logs, which is set to 1
# after seeing such a line, and set to 0 when the first line
# was seen which does not begin with '+'.
#
# A particularly nasty special case is when a single "*" was
# misattributed by the diff to be _inserted before_ a $Log, instead
# of _appended after_ a $Log.
# This is the purpose of the $before_log and $after_log variables:
# if not empty, the state machine expects the next line to begin
# with '+' or '-', respectively, and followed by a $Log.  If this
# expectation is not met, the variable is output.
#
# The variable $plus_minus_adjust contains the number of lines which
# were skipped from the "+" side, so that the correct offset is shown.


# This function gets a hunk header.
#
# It initializes the state variables described above

sub init_hunk {
	my $line = $_[0];
	$current_hunk = "";
	($start_minus, $dummy, $start_plus, $dummy) =
		($line =~ /^\@\@ -(\d+)(,\d+|) \+(\d+)(,\d+|) \@\@/);
	$plus = $minus = $space = 0;
	$skip_logs = 0;
	$before_log = '';
	$after_log = '';

	# we prefer /dev/null as original file name when a file is new
	if ($start_minus eq 0) {
		$current_file =~ s/\n--- .*\n/\n--- \/dev\/null\n/;
	} elsif ($start_plus eq 0) {
		$current_file =~ s/\n\+\+\+ .*\n/\n+++ \/dev\/null\n/;
	}
}

# This function is called whenever there is possibly a hunk to print.
# Nothing is printed if no '+' or '-' lines are left.
# Otherwise, if the file header was not yet shown, it does so now.

sub flush_hunk {
	if (($plus > 0 || $minus > 0) && $current_hunk ne '') {
		if ($current_file ne "") {
			print $current_file;
			$current_file = "";
		}
		$minus += $space;
		$plus += $space;
		print "\@\@ -$start_minus,$minus "
			. "+" . ($start_plus - $start_plus_adjust)
			. ",$plus \@\@\n";
		print $current_hunk;
		$current_hunk = '';
	}
}

# This adds a line to the current hunk and updates $space, $plus or $minus

sub add_line {
	my $line = $_[0];
	$current_hunk .= $line;
	if ($line =~ /^ /) {
		$space++;
	} elsif ($line =~ /^\+/) {
		$plus++;
	} elsif ($line =~ /^-/) {
		$minus++;
	} elsif ($line =~ /^\\/) {
		# do nothing
	} else {
		die "Unexpected line: $line";
	}
}

# This function splits the current hunk into the part before the current
# line, and the part after the current line.

sub skip_line {
	my $line = $_[0];

	if ($start_minus == 0) {
		# This patch adds a new file, just ignore that line
		return;
	} elsif ($start_plus == 0) {
		# This patch removes a file, so include the line nevertheless
		add_line $_;
		return;
	}

	flush_hunk;
	if ($line =~ /^-/) {
		$minus++;
	} elsif ($line =~ /^\+/) {
		$plus++;
		$start_plus_adjust++;
	}
	init_hunk "@@ -" . ($start_minus + $minus + $space)
		. " +" . ($start_plus + $plus + $space)
		. " @@\n";
}

$simple_keyword = "Id|Revision|Author|Date|Source|Header";

# This is the main loop

sub check_file {
	$_ = $_[0];
	$current_file = $_;
	$start_plus_adjust = 0;
	while (<>) {
		if (/^\@\@/) {
			last;
		}
		$current_file .= $_;
	}

	init_hunk $_;

	# check hunks
	while (<>) {
		if ($before_log) {
			if (!/\+.*\$Log.*\$/) {
				add_line $before_log;
			} else {
				skip_line $before_log;
			}
			$before_log = '';
		}

		if ($after_log) {
			if (!/-.*\$Log.*\$/) {
				add_line $after_log;
			} else {
				skip_line $after_log;
			}
			$after_log = '';
		}

		if ($skip_logs) {
			if (/^\+/) {
				skip_line $_;
				$skip_logs = 1;
			} else {
				$skip_logs = 0;
				if (/^ *\*$/) {
					$after_log = $_;
				}
			}
		} elsif (/^\+.*\$($simple_keyword).*\$/) {
			skip_line $_;
		} elsif (/^\@\@.*/) {
			flush_hunk;
			init_hunk $_;
		} elsif (/^diff/) {
			flush_hunk;
			return;
		} elsif (/^-.*\$($simple_keyword).*\$/) {
			# fake new hunk
			skip_line $_;
		} elsif (/^\+ *\*$/) {
			$before_log = $_;
		} elsif (/^([- \+]).*\$Log.*\$/) {
			skip_line $_;
			$skip_logs = 1;
		} else {
			add_line $_;
		}
	}
}

# This loop just shows everything before the first diff, and then hands
# over to check_file whenever it sees a line beginning with "diff".

while (<>) {
	if (/^diff/) {
		do {
			check_file $_;
		} while(/^diff/);
	} else {
		printf $_;
	}
}
flush_hunk;