prepare-commit-msg

#!/usr/bin/env node
var exec = require('child_process').exec,
    util = require('util'),
    fs = require('fs'),
    contents = null,
    branch, desc;

// expect .git/COMMIT_EDITMSG
if(/COMMIT_EDITMSG/g.test(process.argv[2])){
    // look for current branch name
    branch = exec("git branch | grep '*'",
      function (err, stdout, stderr) {
        if(err){
            // git branch will fail if initial commit has not been done,
            // so we can safely skip this hook
            process.exit(0);
        }

        // opens .git/COMMIT_EDITMSG
        contents = fs.readFileSync(process.argv[2]);

        // trims extra characters from start/end of line
        var name = stdout.replace('* ','').replace('\n','');

        // If the branch has a description, pull that
        desc = exec('git config branch.'+ name +'.description',
            function(err, stdout, stderr){
                // don't handle errors (because we write out branch anyway)

                // we found a description, add to 'name'
                if(stdout){ name = util.format('%s (%s)', name, stdout.replace(/\n/g,'')); }

                // '(no branch)' indicates we are in a rebase or other non-HEAD scenario
                if(name !== '(no branch)'){
                    // matches: /ABC-123, /aBc-123, /abc-123, /AbC-123, /abc-123-456
                    // Begins with slash because prefix is always: feature, bugfix, chore...
                    // Project ID is always alpha
                    // Issue ID is always numeric
                    var jiraIssue = /\/[a-zA-Z]+([-][0-9]+)+/;

                    if (jiraIssue.test(name)) {
                        // Extract issue(s) from branch name
                        var issueLine = jiraIssue.exec(name)[0].substring(1).toUpperCase().split('-');
                        name = [issueLine[0], issueLine[1]].join('-');

                        // Append for multiple issues
                        for(var i = 2; i < issueLine.length; i++) {
                          name += ',' + [issueLine[0], issueLine[i]].join('-');
                        }
                    }
                    else {
                        process.exit(0);
                    }

                    // Append name to original contents.
                    contents = util.format('[%s] %s', name, contents);

                    // write contents back out to .git/COMMIT_EDITMSG
                    fs.writeFileSync(process.argv[2], contents);
                    process.exit(0);

                } else {
                    process.exit(0);
                }
        });
    });
}