a better git merge-tree for printing merge conflicts

git-merge-tree.pl

#!/usr/bin/perl

use strict;
use Term::ANSIColor;

$ARGV[1] = $ARGV[1] || 'HEAD';

my $mb = `git merge-base $ARGV[0] $ARGV[1]`;

# trim ()
$mb =~ s/^\s+//;
$mb =~ s/\s+$//;

my $cmd = "git merge-tree $mb $ARGV[1] $ARGV[0]";

my $str = `$cmd`."\ny";

my $regex = qr/^(changed in both|removed in local|removed in remote|added in both)\n([\s\S\r]*?)(?=\n[rcyam])/mp;

my @files = ();
while ( $str =~ /$regex/g ) {
  if ($1 eq "changed in both" or $1 eq "added in both") {
    my $reason = $1;
    my $str2 = $2;
    my $rg2 = qr/^\+<<<<<<<.*^\+======.*^\+>>>>>>>/msp;
    
    if ($str2 =~ /$rg2/g) {
      my $rg_getfile = qr/^  our\s+\w+\s+\w+\s(\S+)/msp;
      if ($str2 =~ /$rg_getfile/) {
        if ($reason eq "changed in both") {
          push(@files, "both modified:   $1\n");
          # push(@files, colored("\nboth modified:", "red")."   $1");
        } else {
          # added in both
          push(@files, "both added:      $1\n");
          # push(@files, colored("\n$reason:", "red")."   $1");
        }
      }
    }
    
  } elsif ($1 eq "removed in local") {
    my $str2 = $2;
    my $rg2 = qr/^  base\s+\w+\s+(\w+).*^  their\s+\w+\s(\w+)\s(\S+)/msp;

    if ( $str2 =~ /$rg2/g ) {
      if ($1 ne $2) {
        push(@files, "deleted by us:   $3\n")
        # push(@files, colored("\ndeleted by us:", "red")."   $3")
      } 
    } else {
      push(@files, "couldn't parse changes from 'removed in local'\n")
    }
  } elsif ($1 eq "removed in remote") {
    my $str2 = $2;
    my $rg2 = qr/^  base\s+\w+\s+(\w+).*^  our\s+\w+\s(\w+)\s(\S+)/msp;

    if ($str2 =~ /$rg2/g) {
      if ($1 ne $2) {
        push(@files, "deleted by them: $3\n")
        # push(@files, colored("\ndeleted by them:", "red")." $3")
      }
    }
  }
}

print @files

Usage examples:

preview merge conflicts that will happen merging origin/master into HEAD:

git-merge-tree.pl origin/master

git-merge-tree.pl master output before merge:

git status after git merge master:

review merge conflicts that had to be resolved in <merge-commit-sha>:

git-merge-tree.pl origin/master <merge-commit-sha>^

NOTE: unfortunately renames will show up as deleted from this script, when they would actually be auto-merged.