initial commit

10 files changed, 388 insertions, 0 deletions

diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..c4a847d
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1 @@
+/result
diff --git a/LICENSE b/LICENSE
new file mode 100644
index 0000000..7389b02
--- /dev/null
+++ b/LICENSE
@@ -0,0 +1,19 @@
+Copyright (c) 2025 Martin Fischer <martin@push-f.com>
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.
diff --git a/README.md b/README.md
new file mode 100644
index 0000000..d6ebb75
--- /dev/null
+++ b/README.md
@@ -0,0 +1,11 @@
+# git-grep-exporter
+
+Prometheus metrics for how many lines in certain git repos match certain regular expressions.
+
+Only the HEAD of the repositories will be grepped.
+The metrics are named `{pattern}_lines` and have `repo` labels.
+
+I made this to track the amount of TODO and FIXME comments in my repositories
+because often while fixing one TODO I end up writing two more and it feels like
+it's never ending but surely there's an end? The patterns are fully configurable
+so you could also use this to track curse words ... or something else?
diff --git a/default.nix b/default.nix
new file mode 100644
index 0000000..27d801c
--- /dev/null
+++ b/default.nix
@@ -0,0 +1,15 @@
+{ pkgs ? import <nixpkgs> {} }:
+
+pkgs.buildGoModule {
+  pname = "git-grep-exporter";
+  version = "0+git";
+  src = pkgs.lib.cleanSource ./.;
+  vendorHash = (import ./hashes.nix).vendor;
+
+  nativeBuildInputs = with pkgs; [makeWrapper];
+
+  postInstall = ''
+    wrapProgram $out/bin/git-grep-exporter \
+      --prefix PATH : ${pkgs.lib.makeBinPath [pkgs.gitMinimal]}
+  '';
+}
diff --git a/go.mod b/go.mod
new file mode 100644
index 0000000..aa1f500
--- /dev/null
+++ b/go.mod
@@ -0,0 +1,22 @@
+module push-f.com/git-grep-exporter
+
+go 1.25.4
+
+require (
+	github.com/alecthomas/kong v1.13.0
+	github.com/google/go-cmp v0.7.0
+	github.com/prometheus/client_golang v1.23.2
+	github.com/prometheus/common v0.66.1
+)
+
+require (
+	github.com/beorn7/perks v1.0.1 // indirect
+	github.com/cespare/xxhash/v2 v2.3.0 // indirect
+	github.com/kr/text v0.2.0 // indirect
+	github.com/munnerz/goautoneg v0.0.0-20191010083416-a7dc8b61c822 // indirect
+	github.com/prometheus/client_model v0.6.2 // indirect
+	github.com/prometheus/procfs v0.16.1 // indirect
+	go.yaml.in/yaml/v2 v2.4.2 // indirect
+	golang.org/x/sys v0.35.0 // indirect
+	google.golang.org/protobuf v1.36.8 // indirect
+)
diff --git a/go.sum b/go.sum
new file mode 100644
index 0000000..46a5365
--- /dev/null
+++ b/go.sum
@@ -0,0 +1,54 @@
+github.com/alecthomas/assert/v2 v2.11.0 h1:2Q9r3ki8+JYXvGsDyBXwH3LcJ+WK5D0gc5E8vS6K3D0=
+github.com/alecthomas/assert/v2 v2.11.0/go.mod h1:Bze95FyfUr7x34QZrjL+XP+0qgp/zg8yS+TtBj1WA3k=
+github.com/alecthomas/kong v1.13.0 h1:5e/7XC3ugvhP1DQBmTS+WuHtCbcv44hsohMgcvVxSrA=
+github.com/alecthomas/kong v1.13.0/go.mod h1:wrlbXem1CWqUV5Vbmss5ISYhsVPkBb1Yo7YKJghju2I=
+github.com/alecthomas/repr v0.5.2 h1:SU73FTI9D1P5UNtvseffFSGmdNci/O6RsqzeXJtP0Qs=
+github.com/alecthomas/repr v0.5.2/go.mod h1:Fr0507jx4eOXV7AlPV6AVZLYrLIuIeSOWtW57eE/O/4=
+github.com/beorn7/perks v1.0.1 h1:VlbKKnNfV8bJzeqoa4cOKqO6bYr3WgKZxO8Z16+hsOM=
+github.com/beorn7/perks v1.0.1/go.mod h1:G2ZrVWU2WbWT9wwq4/hrbKbnv/1ERSJQ0ibhJ6rlkpw=
+github.com/cespare/xxhash/v2 v2.3.0 h1:UL815xU9SqsFlibzuggzjXhog7bL6oX9BbNZnL2UFvs=
+github.com/cespare/xxhash/v2 v2.3.0/go.mod h1:VGX0DQ3Q6kWi7AoAeZDth3/j3BFtOZR5XLFGgcrjCOs=
+github.com/creack/pty v1.1.9/go.mod h1:oKZEueFk5CKHvIhNR5MUki03XCEU+Q6VDXinZuGJ33E=
+github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
+github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/google/go-cmp v0.7.0 h1:wk8382ETsv4JYUZwIsn6YpYiWiBsYLSJiTsyBybVuN8=
+github.com/google/go-cmp v0.7.0/go.mod h1:pXiqmnSA92OHEEa9HXL2W4E7lf9JzCmGVUdgjX3N/iU=
+github.com/hexops/gotextdiff v1.0.3 h1:gitA9+qJrrTCsiCl7+kh75nPqQt1cx4ZkudSTLoUqJM=
+github.com/hexops/gotextdiff v1.0.3/go.mod h1:pSWU5MAI3yDq+fZBTazCSJysOMbxWL1BSow5/V2vxeg=
+github.com/klauspost/compress v1.18.0 h1:c/Cqfb0r+Yi+JtIEq73FWXVkRonBlf0CRNYc8Zttxdo=
+github.com/klauspost/compress v1.18.0/go.mod h1:2Pp+KzxcywXVXMr50+X0Q/Lsb43OQHYWRCY2AiWywWQ=
+github.com/kr/pretty v0.3.1 h1:flRD4NNwYAUpkphVc1HcthR4KEIFJ65n8Mw5qdRn3LE=
+github.com/kr/pretty v0.3.1/go.mod h1:hoEshYVHaxMs3cyo3Yncou5ZscifuDolrwPKZanG3xk=
+github.com/kr/text v0.2.0 h1:5Nx0Ya0ZqY2ygV366QzturHI13Jq95ApcVaJBhpS+AY=
+github.com/kr/text v0.2.0/go.mod h1:eLer722TekiGuMkidMxC/pM04lWEeraHUUmBw8l2grE=
+github.com/kylelemons/godebug v1.1.0 h1:RPNrshWIDI6G2gRW9EHilWtl7Z6Sb1BR0xunSBf0SNc=
+github.com/kylelemons/godebug v1.1.0/go.mod h1:9/0rRGxNHcop5bhtWyNeEfOS8JIWk580+fNqagV/RAw=
+github.com/munnerz/goautoneg v0.0.0-20191010083416-a7dc8b61c822 h1:C3w9PqII01/Oq1c1nUAm88MOHcQC9l5mIlSMApZMrHA=
+github.com/munnerz/goautoneg v0.0.0-20191010083416-a7dc8b61c822/go.mod h1:+n7T8mK8HuQTcFwEeznm/DIxMOiR9yIdICNftLE1DvQ=
+github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
+github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
+github.com/prometheus/client_golang v1.23.2 h1:Je96obch5RDVy3FDMndoUsjAhG5Edi49h0RJWRi/o0o=
+github.com/prometheus/client_golang v1.23.2/go.mod h1:Tb1a6LWHB3/SPIzCoaDXI4I8UHKeFTEQ1YCr+0Gyqmg=
+github.com/prometheus/client_model v0.6.2 h1:oBsgwpGs7iVziMvrGhE53c/GrLUsZdHnqNwqPLxwZyk=
+github.com/prometheus/client_model v0.6.2/go.mod h1:y3m2F6Gdpfy6Ut/GBsUqTWZqCUvMVzSfMLjcu6wAwpE=
+github.com/prometheus/common v0.66.1 h1:h5E0h5/Y8niHc5DlaLlWLArTQI7tMrsfQjHV+d9ZoGs=
+github.com/prometheus/common v0.66.1/go.mod h1:gcaUsgf3KfRSwHY4dIMXLPV0K/Wg1oZ8+SbZk/HH/dA=
+github.com/prometheus/procfs v0.16.1 h1:hZ15bTNuirocR6u0JZ6BAHHmwS1p8B4P6MRqxtzMyRg=
+github.com/prometheus/procfs v0.16.1/go.mod h1:teAbpZRB1iIAJYREa1LsoWUXykVXA1KlTmWl8x/U+Is=
+github.com/rogpeppe/go-internal v1.10.0 h1:TMyTOH3F/DB16zRVcYyreMH6GnZZrwQVAoYjRBZyWFQ=
+github.com/rogpeppe/go-internal v1.10.0/go.mod h1:UQnix2H7Ngw/k4C5ijL5+65zddjncjaFoBhdsK/akog=
+github.com/stretchr/testify v1.11.1 h1:7s2iGBzp5EwR7/aIZr8ao5+dra3wiQyKjjFuvgVKu7U=
+github.com/stretchr/testify v1.11.1/go.mod h1:wZwfW3scLgRK+23gO65QZefKpKQRnfz6sD981Nm4B6U=
+go.uber.org/goleak v1.3.0 h1:2K3zAYmnTNqV73imy9J1T3WC+gmCePx2hEGkimedGto=
+go.uber.org/goleak v1.3.0/go.mod h1:CoHD4mav9JJNrW/WLlf7HGZPjdw8EucARQHekz1X6bE=
+go.yaml.in/yaml/v2 v2.4.2 h1:DzmwEr2rDGHl7lsFgAHxmNz/1NlQ7xLIrlN2h5d1eGI=
+go.yaml.in/yaml/v2 v2.4.2/go.mod h1:081UH+NErpNdqlCXm3TtEran0rJZGxAYx9hb/ELlsPU=
+golang.org/x/sys v0.35.0 h1:vz1N37gP5bs89s7He8XuIYXpyY0+QlsKmzipCbUtyxI=
+golang.org/x/sys v0.35.0/go.mod h1:BJP2sWEmIv4KK5OTEluFJCKSidICx8ciO85XgH3Ak8k=
+google.golang.org/protobuf v1.36.8 h1:xHScyCOEuuwZEc6UtSOvPbAT4zRh0xcNRYekJwfqyMc=
+google.golang.org/protobuf v1.36.8/go.mod h1:fuxRtAxBytpl4zzqUh6/eyUujkJdNiuEkXntxiD/uRU=
+gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
+gopkg.in/check.v1 v1.0.0-20201130134442-10cb98267c6c h1:Hei/4ADfdWqJk1ZMxUNpqntNwaWcugrBjAiHlqqRiVk=
+gopkg.in/check.v1 v1.0.0-20201130134442-10cb98267c6c/go.mod h1:JHkPIbrfpd72SG/EVd6muEfDQjcINNoR0C8j2r3qZ4Q=
+gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=
+gopkg.in/yaml.v3 v3.0.1/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
diff --git a/hashes.nix b/hashes.nix
new file mode 100644
index 0000000..4b7d66b
--- /dev/null
+++ b/hashes.nix
@@ -0,0 +1,3 @@
+{
+  vendor = "sha256-IO+MeOuwXcbKbLUkXFv6aJYfymbCd9kZXOyLMPAARLE=";
+}
diff --git a/main.go b/main.go
new file mode 100644
index 0000000..919fe24
--- /dev/null
+++ b/main.go
@@ -0,0 +1,149 @@
+package main
+
+import (
+	"bufio"
+	"bytes"
+	"encoding/json"
+	"fmt"
+	"log/slog"
+	"maps"
+	"net/http"
+	"os"
+	"os/exec"
+	"regexp"
+	"slices"
+	"strings"
+	"time"
+
+	"github.com/alecthomas/kong"
+	"github.com/prometheus/client_golang/prometheus"
+	"github.com/prometheus/client_golang/prometheus/promhttp"
+)
+
+type Args struct {
+	Port     int           `help:"Port to listen on" short:"p" default:"8888" env:"PORT"`
+	Repos    StringMap     `placeholder:"{\"name\": \"path\", ...}" required:"" help:"Repositories to be grepped" env:"REPOS"`
+	Patterns StringMap     `placeholder:"{\"name\": \"regex\", ...}" required:"" help:"Patterns to be grepped for" env:"PATTERNS"`
+	Interval time.Duration `help:"How often the repos should be grepped (units: s,m,h for seconds, minutes, hours)" default:"10m" env:"INTERVAL"`
+}
+
+type StringMap map[string]string
+
+func (p *StringMap) UnmarshalJSON(data []byte) error {
+	stringMap := (*map[string]string)(p)
+	return json.Unmarshal(data, &stringMap)
+}
+
+func main() {
+	logger := slog.New(slog.NewTextHandler(os.Stderr, &slog.HandlerOptions{
+		Level: slog.LevelDebug,
+	}))
+	slog.SetDefault(logger)
+
+	var args Args
+	ctx := kong.Parse(&args, kong.Description(
+		"Prometheus metrics for how many lines in certain git repos match certain regular expressions.\n\n"+
+			"Only the HEAD of the repositories will be grepped.",
+	))
+
+	http.Handle("/metrics", promhttp.Handler())
+
+	te, err := newGitGrepExporter(args.Repos, args.Patterns, prometheus.DefaultRegisterer)
+	ctx.FatalIfErrorf(err)
+
+	go func() {
+		ticker := time.NewTicker(args.Interval)
+		defer ticker.Stop()
+
+		// execute immediately on start
+		te.grepRepos()
+
+		for range ticker.C {
+			te.grepRepos()
+		}
+	}()
+
+	slog.Info("starting", "repos", args.Repos, "patterns", args.Patterns, "interval", args.Interval)
+	slog.Info(fmt.Sprintf("serving metrics at http://localhost:%d/metrics", args.Port))
+	http.ListenAndServe(fmt.Sprintf(":%d", args.Port), nil)
+}
+
+type GitGrepExporter struct {
+	repos           map[string]string
+	gauges          map[string]*prometheus.GaugeVec
+	regexes         map[string]*regexp.Regexp
+	combinedPattern string
+}
+
+func newGitGrepExporter(repos map[string]string, patterns map[string]string, reg prometheus.Registerer) (*GitGrepExporter, error) {
+	if len(repos) == 0 {
+		return nil, fmt.Errorf("no repositories specified")
+	}
+	if len(patterns) == 0 {
+		return nil, fmt.Errorf("no patterns specified")
+	}
+
+	gauges := map[string]*prometheus.GaugeVec{}
+	regexes := map[string]*regexp.Regexp{}
+
+	for name, pattern := range patterns {
+		gauges[name] = prometheus.NewGaugeVec(prometheus.GaugeOpts{
+			Name: fmt.Sprintf("%s_lines", name),
+		}, []string{"repo"})
+		reg.MustRegister(gauges[name])
+		regexes[name] = regexp.MustCompile(pattern)
+	}
+
+	return &GitGrepExporter{repos, gauges, regexes, strings.Join(slices.Collect(maps.Values(patterns)), "|")}, nil
+}
+
+func (g *GitGrepExporter) grepRepos() {
+	for name, path := range g.repos {
+		slog.Info("starting grep", "path", path)
+		g.grepRepo(name)
+		slog.Info("finished grep", "path", path)
+	}
+}
+
+func (g *GitGrepExporter) grepRepo(name string) {
+	path := g.repos[name]
+	output, err := run("git", "-C", path, "grep", "-hE", g.combinedPattern, "HEAD")
+
+	if err != nil {
+		if exitErr, ok := err.(*exec.ExitError); ok {
+			if exitErr.ExitCode() == 1 {
+				// no matches found
+
+				for _, gauge := range g.gauges {
+					gauge.With(map[string]string{"repo": name}).Set(0)
+				}
+				return
+			}
+
+			slog.Error("git grep failed", "stderr", string(output))
+			return
+		}
+
+		slog.Error("failed to execute git grep", "error", err)
+		return
+	}
+
+	scanner := bufio.NewScanner(bytes.NewReader(output))
+	counts := map[string]float64{}
+	for scanner.Scan() {
+		line := scanner.Text()
+		for word, regex := range g.regexes {
+			if regex.FindString(line) != "" {
+				counts[word] += 1
+			}
+		}
+	}
+	for word, gauge := range g.gauges {
+		gauge.With(map[string]string{"repo": name}).Set(counts[word])
+	}
+}
+
+var run = func(name string, args ...string) ([]byte, error) {
+	cmd := exec.Command(name, args...)
+	return cmd.CombinedOutput()
+}
diff --git a/main_test.go b/main_test.go
new file mode 100644
index 0000000..bd5130a
--- /dev/null
+++ b/main_test.go
@@ -0,0 +1,63 @@
+package main
+
+import (
+	"log"
+	"strings"
+	"testing"
+
+	"github.com/google/go-cmp/cmp"
+	"github.com/prometheus/client_golang/prometheus"
+	"github.com/prometheus/common/expfmt"
+)
+
+func TestGrepRepo(t *testing.T) {
+	repos := map[string]string{"project1": "/srv/repos/project1"}
+	patterns := map[string]string{"match": "\\bMATCH\\b", "match_start": "^MATCH"}
+	reg := prometheus.NewRegistry()
+	te, err := newGitGrepExporter(repos, patterns, reg)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	run = func(name string, args ...string) ([]byte, error) {
+		return []byte(
+			"not a match\n" +
+				"MATCH can be at the start\n" +
+				"here MATCH is in the middle\n" +
+				"the end can also be MATCH\n" +
+				"MATCH, MATCH counts only once\n",
+		), nil
+	}
+
+	te.grepRepo("project1")
+
+	want := "# HELP match_lines \n" +
+		"# TYPE match_lines gauge\n" +
+		"match_lines{repo=\"project1\"} 4\n" +
+		"# HELP match_start_lines \n" +
+		"# TYPE match_start_lines gauge\n" +
+		"match_start_lines{repo=\"project1\"} 2\n"
+
+	if diff := cmp.Diff(collectMetrics(reg), want); diff != "" {
+		t.Errorf("unexpected metrics: %v", diff)
+	}
+}
+
+func collectMetrics(reg *prometheus.Registry) string {
+	mfs, done, err := prometheus.ToTransactionalGatherer(reg).Gather()
+	if err != nil {
+		log.Fatal(err)
+	}
+	defer done()
+
+	var buf strings.Builder
+	enc := expfmt.NewEncoder(&buf, expfmt.NewFormat(expfmt.TypeTextPlain))
+
+	for _, mf := range mfs {
+		err := enc.Encode(mf)
+		if err != nil {
+			log.Fatal(err)
+		}
+	}
+	return buf.String()
+}
diff --git a/service.nix b/service.nix
new file mode 100644
index 0000000..0b5aa91
--- /dev/null
+++ b/service.nix
@@ -0,0 +1,51 @@
+{ config, lib, pkgs, ... }:
+
+let
+  git_grep_exporter = pkgs.callPackage ./default.nix {};
+  cfg = config.services.gitGrepExporter;
+in
+{
+  options.services.gitGrepExporter = {
+    enable = lib.mkEnableOption "git-grep-exporter";
+
+    port = lib.mkOption {
+      type = lib.types.int;
+    };
+
+    patterns = lib.mkOption {
+      type = lib.types.attrsOf lib.types.str;
+    };
+
+    repos = lib.mkOption {
+      type = lib.types.attrsOf lib.types.str;
+    };
+
+    extraGroups = lib.mkOption {
+      type = lib.types.listOf lib.types.str;
+      default = [];
+    };
+
+    interval = lib.mkOption {
+      type = lib.types.nullOr lib.types.str;
+      default = "10m";
+    };
+  };
+
+  config = lib.mkIf cfg.enable {
+    systemd.services.git-grep-exporter = {
+      serviceConfig = {
+        DynamicUser = true;
+        SupplementaryGroups = cfg.extraGroups;
+        ExecStart = "${git_grep_exporter}/bin/git-grep-exporter";
+      };
+      environment = {
+        PORT = toString cfg.port;
+        REPOS = builtins.toJSON cfg.repos;
+        PATTERNS = builtins.toJSON cfg.patterns;
+        INTERVAL = cfg.interval;
+      };
+
+      wantedBy = ["multi-user.target"];
+    };
+  };
+}