feat(option): add --base to specify a base commit (#6)

README.md

@@ -28,6 +28,7 @@
   - [Run only those benchmarks matching a regular expression](#run-only-those-benchmarks-matching-a-regular-expression)
   - [Show only benchmarks with worse score](#show-only-benchmarks-with-worse-score)
   - [Specify a threshold](#specify-a-threshold)
+  - [Specify a base commit compared with HEAD](#specify-a-base-commit-compared-with-head)
 - [Usage](#usage)
 - [Q&A](#qa)
   - [A result of benchmarks is unstable](#a-result-of-benchmarks-is-unstable)
@@ -217,6 +218,13 @@ The following option means the program fails if a benchmark score gets worse tha
 $ cob -threshold 0.5 ./...
 ```
 
+## Specify a base commit compared with HEAD
+By default, `cob` uses `HEAD~1`. If you compare benchmarks with different commit, you can use `--base` option.
+
+```
+$ cob --base origin/master ./...
+```
+
 # Usage
 
 ```

config.go

@@ -6,6 +6,7 @@ type config struct {
 	args           []string
 	onlyDegression bool
 	threshold      float64
+	base           string
 	bench          string
 	benchmem       bool
 	benchtime      string
@@ -17,6 +18,7 @@ func newConfig(c *cli.Context) config {
 		args:           c.Args().Slice(),
 		onlyDegression: c.Bool("only-degression"),
 		threshold:      c.Float64("threshold"),
+		base:           c.String("base"),
 		bench:          c.String("bench"),
 		benchmem:       c.Bool("benchmem"),
 		benchtime:      c.String("benchtime"),

main.go

@@ -9,6 +9,8 @@ import (
 	"os/exec"
 	"strings"
 
+	"gopkg.in/src-d/go-git.v4/plumbing"
+
 	"golang.org/x/xerrors"
 
 	"github.com/olekukonko/tablewriter"
@@ -40,6 +42,11 @@ func main() {
 				Usage: "The program fails if the benchmark gets worse than the threshold",
 				Value: 0.2,
 			},
+			&cli.StringFlag{
+				Name:  "base",
+				Usage: "Specify a base commit compared with HEAD",
+				Value: "HEAD~1",
+			},
 			&cli.StringFlag{
 				Name:  "bench",
 				Usage: "Run only those benchmarks matching a regular expression.",
@@ -78,7 +85,7 @@ func run(c config) error {
 		return xerrors.Errorf("unable to get the reference where HEAD is pointing to: %w", err)
 	}
 
-	prev, err := r.ResolveRevision("HEAD~1")
+	prev, err := r.ResolveRevision(plumbing.Revision(c.base))
 	if err != nil {
 		return xerrors.Errorf("unable to resolves revision to corresponding hash: %w", err)
 	}
@@ -104,7 +111,7 @@ func run(c config) error {
 
 	args := prepareBenchArgs(c)
 
-	log.Printf("Run Benchmark: %s %s", prev, "HEAD{@1}")
+	log.Printf("Run Benchmark: %s %s", prev, c.base)
 	prevSet, err := runBenchmark(args)
 	if err != nil {
 		return xerrors.Errorf("failed to run a benchmark: %w", err)