Parse 'git describe' output

parse-git-describe.c

#include <string.h>
#include <stdio.h>
#include <stdlib.h>

static void find_delim(char *s, char **res, int *ix)
{
    for(; *ix && s[*ix] != '-'; *ix -= 1);
    if (*ix) {
        s[*ix] = '\0';
        *res = s + *ix + 1;
    } else {
        *res = s;
    }
}

int main(int argc, char **argv)
{
    char vbuf[4096] = { 0 };
    char *version, *ncommits, *sha;
    FILE *po;
    int buflen;
    char *format;
    int force;
    int ncommits_i;

    if (argc != 2) {
        fprintf(stderr, "Usage: %s <FORMAT>\n", argv[0]);
        exit(EXIT_FAILURE);
    }

    /** Get the output */
    po = popen("git describe --long", "r");
    if (!po) {
        perror("git describe");
        exit(EXIT_FAILURE);
    }

    if (!fgets(vbuf, sizeof(vbuf), po)) {
        fprintf(stderr, "git describe closed stream\n");
        exit(EXIT_FAILURE);
    }
    fclose(po);
    buflen = strlen(vbuf);
    vbuf[buflen-2] = '\0';
    buflen -= 1;

    find_delim(vbuf, &sha, &buflen);
    find_delim(vbuf, &ncommits, &buflen);
    version = vbuf;

    sscanf(ncommits, "%d", &ncommits_i);
    format = argv[1];
    force = *format == 'F';
    if (force) {
        format++;
    }

    if (!force) {
        force = ncommits_i;
    }

    for (; *format; format++) {
        switch (*format) {
            case 'T':
            case 't':
                printf("%s\n", version);
                break;
            case 'N':
            case 'n':
                if (force) {
                    printf("%s\n", ncommits);
                }
                break;
            case 's':
            case 'S':
                if (force) {
                    printf("%s\n", sha);
                }
        }
    }
    return 0;
}

parse-git-describe.pl

#!/usr/bin/perl

use strict;
use warnings;
use Getopt::Long;

my $rv = GetOptions(
    'basetag|t' => \my $PrintBase,
    'ncommits|n' => \my $PrintCount,
    'sha|s' => \my $PrintSHA,
    'force|f' => \my $Force,
    'help|h' => \my $WantHelp);

my $HELPTEXT =
<<EOF;
    -t --basetag    Print base tag
    -n --ncommits   Print number of commits since base
    -s --sha        Print abbreviated SHA1
    -f --force      Always print ncommits/sha, even if HEAD is a tag
EOF

if (!$rv) {
    print $HELPTEXT;
    exit(1);
}
if ($WantHelp) {
    print $HELPTEXT;
    exit(0);
}

my $output = qx(git describe --long);
$output =~ s/\s+$//g;
$output =~ s/^\s+//g;

my @components = split('-', $output);
my $sha = pop @components;
my $ncommits = pop @components;
my $version = join('-', @components);

if ($PrintBase) {
    print "$version\n";
}

if (!$Force) {
    $Force = int($ncommits);
}

if ($PrintSHA && $Force) {
    print "$sha\n";
}

if ($PrintCount && $Force) {
    print "$ncommits\n";
}

parse-git-describe.py

#!/usr/bin/env python
from optparse import OptionParser
from subprocess import Popen, PIPE


op = OptionParser()
op.add_option('--basetag',
              help="Print base tag", action='store_true')
op.add_option('--ncommits',
              help="Print number of commits since tag",
              action='store_true')
op.add_option('--abbrev-sha',
              help="Print abbreviated SHA1",
              action='store_true')
op.add_option('--always-print-extra',
              help="Always print abbrev/ncommits, even if HEAD==tag",
              action='store_true')

options, args = op.parse_args()
stdout, stderr = Popen(['git', 'describe', '--long'], stdout=PIPE).communicate()
components = stdout.strip().split('-')
sha = components.pop()
ncommits = components.pop()
version = "-".join(components)

print_extras = (int(ncommits)) or options.always_print_extra

if options.basetag:
    print version
if options.ncommits and print_extras:
    print ncommits
if options.abbrev_sha and print_extras:
    print sha