Fix GIT_DIFF_TREE_PATTERN wrt number of status letters

[krinklesaurus]

Hi,

we recently saw this failure in our GoCD Pipeline:

The plugin sent a response that could not be understood by Go. Plugin returned with code '500' and the following response: '"Unable to parse git-diff-tree output line: MMMMM\tDockerfile\nFrom output:\n afc1a254a698be419299e6717a6c72c4e365ac8c\nMMMMM\tDockerfile"'

There was a similar issue reported here: ashwanthkumar/gocd-build-github-pull-requests#123 In that case, only 3 Ms were part of the response line, in our case it's 5.

From our investigation it looks like the executed git diff-tree command is

git diff-tree --name-status --root -r -c <revision>

Now according to the git documentation documentation

status is concatenated status characters for each parent

So if a revision has X parents, X status letters are in that line. In that case, the git pattern used here doesn't work anymore since it only accepts up to 3 status letters.

The fix in this PRs is to group anything until the first occurance of a whitespace, then group everything following that whitespace.

Tested with some quick main method:

public static void main(String[] args) {
    final Pattern GIT_DIFF_TREE_PATTERN = Pattern.compile("^([^\\s]+)\\s+(.+)$");

    final String[] resultLines = new String[]{
        "M\tsrc/main/blablabla.json",
        "MMM\tapp/xxx/src/main/webapp/xxxx/xxx.jsp",
        "MMMMM\tDockerfile",
    };

    for(String resultLine : resultLines) {
    Matcher m = GIT_DIFF_TREE_PATTERN.matcher(resultLine);
    if (!m.find()) {
        throw new RuntimeException(String.format("Unable to parse git-diff-tree output line: %s%nFrom output:%n %s", resultLine, String.join(System.lineSeparator())));
    }
    System.err.println(String.format("%s : %s", m.group(1), m.group(2)));
    }
}

[krinklesaurus]

@ashwanthkumar any update?

[chadlwilson]

Unfortunately, even if we merge this, the gocd-build-github-pull-requests plugin has never been updated to use v2.x of this base lib, so there's probably a bit of work there too.

I do have collaborator permissions to merge here, but I can't cut new releases and push to Maven central without @ashwanthkumar help as there isn't GitHub Actions automation.

Is there a possibility of adding a test for this do you think?

[krinklesaurus]

Hey @chadlwilson
sorry I totally missed your answer. I saw that https://github.com/ashwanthkumar/gocd-build-github-pull-requests is using version 1.4 of git-cmd but I don't find the version in this repo. If you point me to the correct revision I would be happy to open the PR again against that version if that helps.

Regarding the test, I'm not familiar with how the sample git directory structure needs to be to cover a merge commit with multiple parents. Even the merge-commit-git-repository is not showing any merge commits to me. The last change to this pattern was approved without any test as well #3 so maybe the existing test coverage is sufficient?

[krinklesaurus]

Hey @chadlwilson

since our GoCD pipelines are still broken, we

• checkout out git-cmd version 1.4
• applied the fix and build git-cmd locally
• incorporated the new git-cmd to gocd-build-github-pull-requests 1.4.0-RC4
• then build the plugin with mvn -Pgithub.pr clean install

Worked out for us. I leave the PR as it is but it doesn't really matter to us anymore 🙂 Thank you