Explain seemingly pointless use of system in difftool
[git/git.git] / git-difftool.perl
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1#!/usr/bin/env perl
2# Copyright (c) 2009 David Aguilar
3#
4# This is a wrapper around the GIT_EXTERNAL_DIFF-compatible
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5# git-difftool--helper script.
6#
7# This script exports GIT_EXTERNAL_DIFF and GIT_PAGER for use by git.
8# GIT_DIFFTOOL_NO_PROMPT, GIT_DIFFTOOL_PROMPT, and GIT_DIFF_TOOL
9# are exported for use by git-difftool--helper.
10#
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11# Any arguments that are unknown to this script are forwarded to 'git diff'.
12
13use strict;
14use warnings;
15use Cwd qw(abs_path);
16use File::Basename qw(dirname);
17
18my $DIR = abs_path(dirname($0));
19
20
21sub usage
22{
23 print << 'USAGE';
8b733222 24usage: git difftool [--tool=<tool>] [-y|--no-prompt] ["git diff" options]
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25USAGE
26 exit 1;
27}
28
29sub setup_environment
30{
31 $ENV{PATH} = "$DIR:$ENV{PATH}";
32 $ENV{GIT_PAGER} = '';
afcbc8e7 33 $ENV{GIT_EXTERNAL_DIFF} = 'git-difftool--helper';
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34}
35
36sub exe
37{
38 my $exe = shift;
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39 if ($^O eq 'MSWin32' || $^O eq 'msys') {
40 return "$exe.exe";
41 }
42 return $exe;
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43}
44
45sub generate_command
46{
47 my @command = (exe('git'), 'diff');
48 my $skip_next = 0;
49 my $idx = -1;
50 for my $arg (@ARGV) {
51 $idx++;
52 if ($skip_next) {
53 $skip_next = 0;
54 next;
55 }
46ae156d 56 if ($arg eq '-t' || $arg eq '--tool') {
5c38ea31 57 usage() if $#ARGV <= $idx;
2464456a 58 $ENV{GIT_DIFF_TOOL} = $ARGV[$idx + 1];
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59 $skip_next = 1;
60 next;
61 }
62 if ($arg =~ /^--tool=/) {
2464456a 63 $ENV{GIT_DIFF_TOOL} = substr($arg, 7);
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64 next;
65 }
8b733222 66 if ($arg eq '-y' || $arg eq '--no-prompt') {
5c38ea31 67 $ENV{GIT_DIFFTOOL_NO_PROMPT} = 'true';
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68 delete $ENV{GIT_DIFFTOOL_PROMPT};
69 next;
70 }
71 if ($arg eq '--prompt') {
72 $ENV{GIT_DIFFTOOL_PROMPT} = 'true';
73 delete $ENV{GIT_DIFFTOOL_NO_PROMPT};
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74 next;
75 }
8b733222 76 if ($arg eq '-h' || $arg eq '--help') {
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77 usage();
78 }
79 push @command, $arg;
80 }
81 return @command
82}
83
84setup_environment();
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85
86# ActiveState Perl for Win32 does not implement POSIX semantics of
87# exec* system call. It just spawns the given executable and finishes
88# the starting program, exiting with code 0.
89# system will at least catch the errors returned by git diff,
90# allowing the caller of git difftool better handling of failures.
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91my $rc = system(generate_command());
92exit($rc | ($rc >> 8));