#!/usr/local/bin/perl

# Merge conflicted ChangeLogs
# tromey Mon Aug 15 1994

# Due to popular demand, I'm posting my ChangeLog auto-merge tool.  Run
# this on your ChangeLog files when an update leaves them conflicted.
# The code is appended.
#
# Usage is:
#
#	cl-merge [-i] file ...
#
# With -i, it works in place (backups put in a ~ file).  Otherwise the
# merged ChangeLog is printed to stdout.
#
# Style comments are welcome.  This is my third perl program ever.
#
# Please report any bugs to me.  I wrote this yesterday, so there are no
# guarantees about its performance.  I recommend checking its output
# carefully.  If you do send a bug report, please includie the failing
# ChangeLog, so I can include it in my test suite.
#
# Tom
# ---
# tromey@busco.lanl.gov             Member, League for Programming Freedom
# Sadism and farce are always inexplicably linked.
#	-- Alexander Theroux

# If '-i' is given, do it in-place.
if ($ARGV[0] eq '-i') {
    shift (@ARGV);
    $^I = '~';
}

$lastkey = '';
$lastval = '';
$conf = 0;
%conflist = ();

$tjd = 0;

# Simple state machine.  The states:
#
# 0	Not in conflict.  Just copy input to output.
# 1	Beginning an entry.  Next non-blank line is key.
# 2	In entry.  Entry beginner transitions to state 1.
while (<>) {
    if (/^<<<</ || /^====/) {
	# Start of a conflict.

	# Copy last key into array.
	if ($lastkey ne '') {
	    $conflist{$lastkey} = $lastval;

	    $lastkey = '';
	    $lastval = '';
	}

	$conf = 1;
    } elsif (/^>>>>/) {
	# End of conflict.  Output.

	# Copy last key into array.
	if ($lastkey ne '') {
	    $conflist{$lastkey} = $lastval;

	    $lastkey = '';
	    $lastval = '';
	}

	foreach (reverse sort clcmp keys %conflist) {
	    print STDERR "doing $_" if $tjd;
	    print $_;
	    print $conflist{$_};
	}

	$lastkey = '';
	$lastval = '';
	$conf = 0;
	%conflist = ();
    } elsif ($conf == 1) {
	# Beginning an entry.  Skip empty lines.  Error if not a real
	# beginner.
	if (/^$/) {
	    # Empty line; just skip at this point.
	} elsif (/^[MTWFS]/) {
	    # Looks like the name of a day; assume opener and move to
	    # "in entry" state.
	    $lastkey = $_;
	    $conf = 2;
	    print STDERR "found $_" if $tjd;
	} else {
	    die ("conflict crosses entry boundaries: $_");
	}
    } elsif ($conf == 2) {
	# In entry.  Copy into variable until we see beginner line.
	if (/^[MTWFS]/) {
	    # Entry beginner line.

	    # Copy last key into array.
	    if ($lastkey ne '') {
		$conflist{$lastkey} = $lastval;

		$lastkey = '';
		$lastval = '';
	    }

	    $lastkey = $_;
	    print STDERR "found $_" if $tjd;
	    $lastval = '';
	} else {
	    $lastval .= $_;
	}
    } else {
	# Just copy.
	print;
    }
}

%months = ('Jan', 0,
	   'Feb', 1,
	   'Mar', 2,
	   'Apr', 3,
	   'May', 4,
	   'Jun', 5,
	   'Jul', 6,
	   'Aug', 7,
	   'Sep', 8,
	   'Oct', 9,
	   'Nov', 10,
	   'Dec', 11);

# Compare ChangeLog time strings like <=>.
#
# 0         1         2         3
# Thu Aug 11 13:22:42 1994  Tom Tromey  (tromey@creche.colorado.edu)
# 0123456789012345678901234567890
#
sub clcmp {
    # First check year.
    $r = substr ($a, 20, 4) <=> substr ($b, 20, 4);

    # Now check month.
    $r = $months{$a} <=> $months{$b} if !$r;

    # Now check day.
    $r = substr ($a, 8, 2) <=> substr ($b, 8, 2) if !$r;

    # Now check time (3 parts).
    $r = substr ($a, 11, 2) <=> substr ($b, 11, 2) if !$r;
    $r = substr ($a, 14, 2) <=> substr ($b, 14, 2) if !$r;
    $r = substr ($a, 17, 2) <=> substr ($b, 17, 2) if !$r;

    $r;
}