Get top contributors for a source file of a git repo.

excludedCommits

// ==== phobos
// git log --grep='convert docstring examples to unittests' --pretty=%H
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// ==== dmd
// cdmd => ddmd
aeb7e88f9fafd6be7e451d6f42788a744bac979b
// first tarball drops `git log --reverse --format=%H | head -n 160`
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module_contributors.d

import std.algorithm, std.conv, std.datetime, std.file, std.path, std.stdio, std.string,
    std.process;

// exclude reformatting commits that aren't catched by --ignore-all-space
alias SetVal = void[0];
immutable SetVal[string] excludedCommits;

shared static this()
{
    SetVal[string] aa;
    foreach (line; File(thisExePath.dirName.buildPath("excludedCommits"), "r").byLine)
    {
        if (line.startsWith("//"))
            continue;
        aa[line.idup] = SetVal.init;
    }
    excludedCommits = cast(immutable) aa;
}

float[string] getContributions(string path)
{
    immutable now = Clock.currTime;
    float[string] contributions;
    auto pipe = pipeProcess(["git", "blame", "--line-porcelain", "-w", "--", path]);
    string author;
    size_t i;
    bool excluded;
    foreach (line; pipe.stdout.byLine)
    {
        //writeln(line);
        switch (i)
        {
        case 0: // hash LO LF N
            excluded = !!(line.splitter().front in excludedCommits);
            ++i;
            break;

        case 1:
            auto parts = line.findSplit(" ");
            switch (parts[0])
            {
            case "author":
                author = parts[2].dup;
                break;

            case "author-mail":
                if (author.empty)
                    writeln(line);
                author ~= " " ~ parts[2];
                break;

            case "author-time":
                immutable authoredAt = parts[2].to!uint.unixTimeToStdTime.SysTime;
                if (!excluded)
                    contributions[author] = contributions.get(author, 0.0f) + score(now - authoredAt);
                break;

            default:
                break;

            case "filename":
                ++i;
                break;
            }
            break;

        case 2: // source line
            i = 0;
            break;

        default:
            assert(0);
        }
    }
    pipe.pid.wait;
    return contributions;
}

enum gravity = 2.0; // how fast the weight of contributions age
/// (additions + deletions) / (age / years + 1) ^^ G
float score(Duration age)
{
    import std.math;

    return pow(age.total!"days" / 365.0 + 1.0f, -gravity);
}

void main(string[] args)
{
    import std.array : array;
    import std.typecons : tuple, Tuple;
    import std.math : isNaN;

    immutable now = Clock.currTime;
    writeln("module,author,score");
    foreach (arg; args[1 .. $])
    {
        Tuple!(string, float)[5] tops;
        auto contribs = getContributions(arg).
            byKeyValue.
            map!(p => tuple(p.key, p.value)).
            topNCopy!((a, b) => a[1] > b[1])(tops[], SortOutput.yes);
        foreach (t; tops[].filter!(t => !t[1].isNaN))
            writeln(arg, ",", t[0], ",", t[1]);
    }
}

Usage

cd dmd
find ./src/ddmd -name '*.[chdimak]' | xargs ../module_contributors/module_contributors | tee ~/dmd_contributors.txt
cd ../druntime
find ./src -name '*.[chdimak]' | xargs ../module_contributors/module_contributors | tee ~/druntime_contributors.txt
cd ../phobos
find . -name '*.[chdimak]' | xargs ../module_contributors/module_contributors | tee ~/phobos_contributors.txt