tools: Simplify gerrit-stats and snippets

Automatically try to infer 'user' from git config.
Default to 'dawn' repo over tint.

Usage:

tools/run snippets
tools/run gerrit-stats

Change-Id: I8c4617101447ac635e753b0a2a0b655ba6c64b54
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/86300
Auto-Submit: Ben Clayton <bclayton@google.com>
Reviewed-by: Corentin Wallez <cwallez@chromium.org>
Commit-Queue: Corentin Wallez <cwallez@chromium.org>

tools/src/cmd/gerrit-stats/main.go

@@ -20,10 +20,12 @@ import (
 	"fmt"
 	"net/url"
 	"os"
+	"os/exec"
 	"regexp"
 	"time"
 
 	"dawn.googlesource.com/dawn/tools/src/gerrit"
+	"dawn.googlesource.com/dawn/tools/src/git"
 )
 
 const yyyymmdd = "2006-01-02"
@@ -33,14 +35,29 @@ var (
 	// username and password for gerrit.
 	gerritUser  = flag.String("gerrit-user", "", "gerrit authentication username")
 	gerritPass  = flag.String("gerrit-pass", "", "gerrit authentication password")
-	repoFlag    = flag.String("repo", "tint", "the project (tint or dawn)")
+	repoFlag    = flag.String("repo", "dawn", "the project (tint or dawn)")
-	userFlag    = flag.String("user", "", "user name / email")
+	userFlag    = flag.String("user", defaultUser(), "user name / email")
 	afterFlag   = flag.String("after", "", "start date")
 	beforeFlag  = flag.String("before", "", "end date")
 	daysFlag    = flag.Int("days", 182, "interval in days (used if --after is not specified)")
 	verboseFlag = flag.Bool("v", false, "verbose mode - lists all the changes")
 )
 
+func defaultUser() string {
+	if gitExe, err := exec.LookPath("git"); err == nil {
+		if g, err := git.New(gitExe); err == nil {
+			if cwd, err := os.Getwd(); err == nil {
+				if r, err := g.Open(cwd); err == nil {
+					if cfg, err := r.Config(nil); err == nil {
+						return cfg["user.email"]
+					}
+				}
+			}
+		}
+	}
+	return ""
+}
+
 func main() {
 	flag.Parse()
 	if err := run(); err != nil {

tools/src/cmd/snippets/main.go

@@ -19,10 +19,12 @@ import (
 	"flag"
 	"fmt"
 	"os"
+	"os/exec"
 	"strings"
 	"time"
 
 	"dawn.googlesource.com/dawn/tools/src/gerrit"
+	"dawn.googlesource.com/dawn/tools/src/git"
 )
 
 const yyyymmdd = "2006-01-02"
@@ -32,12 +34,27 @@ var (
 	// username and password for gerrit.
 	gerritUser = flag.String("gerrit-user", "", "gerrit authentication username")
 	gerritPass = flag.String("gerrit-pass", "", "gerrit authentication password")
-	userFlag   = flag.String("user", "", "user name / email")
+	userFlag   = flag.String("user", defaultUser(), "user name / email")
 	afterFlag  = flag.String("after", "", "start date")
 	beforeFlag = flag.String("before", "", "end date")
 	daysFlag   = flag.Int("days", 7, "interval in days (used if --after is not specified)")
 )
 
+func defaultUser() string {
+	if gitExe, err := exec.LookPath("git"); err == nil {
+		if g, err := git.New(gitExe); err == nil {
+			if cwd, err := os.Getwd(); err == nil {
+				if r, err := g.Open(cwd); err == nil {
+					if cfg, err := r.Config(nil); err == nil {
+						return cfg["user.email"]
+					}
+				}
+			}
+		}
+	}
+	return ""
+}
+
 func main() {
 	flag.Parse()
 	if err := run(); err != nil {

tools/src/git/git.go

@@ -306,6 +306,33 @@ func (r Repository) Log(opt *LogOptions) ([]CommitInfo, error) {
 	return parseLog(out)
 }
 
+// Optional settings for Repository.ConfigOptions
+type ConfigOptions struct {
+	// Timeout for the operation
+	Timeout time.Duration
+}
+
+// Config returns the git configuration values for the repo
+func (r Repository) Config(opt *ConfigOptions) (map[string]string, error) {
+	if opt == nil {
+		opt = &ConfigOptions{}
+	}
+	text, err := r.run(opt.Timeout, "config", "-l")
+	if err != nil {
+		return nil, err
+	}
+	lines := strings.Split(text, "\n")
+	out := make(map[string]string, len(lines))
+	for _, line := range lines {
+		idx := strings.Index(line, "=")
+		if idx > 0 {
+			key, value := line[:idx], line[idx+1:]
+			out[key] = value
+		}
+	}
+	return out, nil
+}
+
 func (r Repository) run(timeout time.Duration, args ...string) (string, error) {
 	return r.Git.run(r.Path, timeout, args...)
 }