Make fallback tag configurable

Makefile

@@ -14,9 +14,6 @@ VERSION := $(shell git describe --tags --always --dirty)
 run:
 	go run .
 
-run-watch:
-	watch -n1 go run .
-
 build:
 	CGO_ENABLED=0 GOOS=linux GOARCH=amd64 go build -o git-describe-semver-linux-amd64 .
 	CGO_ENABLED=0 GOOS=darwin GOARCH=amd64 go build -o git-describe-semver-darwin-amd64 .

README.md

@@ -17,7 +17,7 @@ Corresponding git tag | git describe --tags | git-describe-semver
 
 ```bash
 cd my-git-directory
-wget -q https://github.com/choffmeister/git-describe-semver/releases/download/v0.0.2/git-describe-semver-linux-amd64
+wget -q https://github.com/choffmeister/git-describe-semver/releases/download/v0.1.0/git-describe-semver-linux-amd64
 chmod +x git-describe-semver-linux-amd64
 ./git-describe-semver-linux-amd64
 ```

main.go

@@ -1,6 +1,7 @@
 package main
 
 import (
+	"flag"
 	"fmt"
 	"log"
 	"os"
@@ -10,18 +11,16 @@ import (
 )
 
 // GenerateVersion ...
-func GenerateVersion(tagName string, counter int, headHash string) (*string, error) {
+func GenerateVersion(tagName string, counter int, headHash string, fallbackTagName string) (*string, error) {
 	devPreRelease := []string{"dev", strconv.Itoa(counter)}
 	buildMetadata := []string{"g" + (headHash)[0:7]}
 	if tagName == "" {
-		version := SemVer{
-			Prefix:        "v",
-			Major:         0,
-			Minor:         0,
-			Patch:         0,
-			PreRelease:    devPreRelease,
-			BuildMetadata: buildMetadata,
+		version := SemVerParse(fallbackTagName)
+		if version == nil {
+			return nil, fmt.Errorf("unable to parse fallback tag")
 		}
+		version.PreRelease = devPreRelease
+		version.BuildMetadata = buildMetadata
 		result := version.String()
 		return &result, nil
 	}
@@ -57,28 +56,31 @@ func GenerateVersion(tagName string, counter int, headHash string) (*string, err
 }
 
 // Run ...
-func Run(dir string) (*string, error) {
+func Run(dir string, fallback string) (*string, error) {
 	repo, err := git.PlainOpen(dir)
 	if err != nil {
 		return nil, fmt.Errorf("unable to open git repository: %v", err)
 	}
 	tagName, counter, headHash, err := GitDescribe(*repo)
 	if err != nil {
-		return nil, fmt.Errorf("unable to find head: %v", err)
+		return nil, fmt.Errorf("unable to describe commit: %v", err)
 	}
-	result, err := GenerateVersion(*tagName, *counter, *headHash)
+	result, err := GenerateVersion(*tagName, *counter, *headHash, fallback)
 	if err != nil {
 		return nil, fmt.Errorf("unable to generate version: %v", err)
 	}
 	return result, nil
 }
 
 func main() {
+	fallback := flag.String("fallback", "", "The first version to fallback to should there be no tag")
+	flag.Parse()
+
 	dir, err := os.Getwd()
 	if err != nil {
 		log.Fatalf("unable to determine current directory: %v\n", err)
 	}
-	result, err := Run(dir)
+	result, err := Run(dir, *fallback)
 	if err != nil {
 		log.Fatalf("unable to generate version: %v\n", err)
 	}

main_test.go

@@ -10,43 +10,48 @@ import (
 
 func TestGenerateVersion(t *testing.T) {
 	assert := assert.New(t)
-	test := func(inputTagName string, inputCounter int, inputHeadHash string, expected string) {
-		actual, err := GenerateVersion(inputTagName, inputCounter, inputHeadHash)
+	test := func(inputTagName string, inputCounter int, inputHeadHash string, inputFallback string, expected string) {
+		actual, err := GenerateVersion(inputTagName, inputCounter, inputHeadHash, inputFallback)
 		if assert.NoError(err) {
 			assert.Equal(expected, *actual)
 
 		}
 	}
 
-	test("0.0.0", 0, "abc1234", "0.0.0")
-	test("0.0.0", 1, "abc1234", "0.0.1-dev.1+gabc1234")
-	test("0.0.0-rc1", 1, "abc1234", "0.0.0-rc1.dev.1+gabc1234")
-	test("0.0.0-rc.1", 1, "abc1234", "0.0.0-rc.1.dev.1+gabc1234")
-	test("0.0.0-rc.1+foobar", 1, "abc1234", "0.0.0-rc.1.dev.1+gabc1234")
-	test("", 1, "abc1234", "v0.0.0-dev.1+gabc1234")
+	test("0.0.0", 0, "abc1234", "", "0.0.0")
+	test("0.0.0", 1, "abc1234", "", "0.0.1-dev.1+gabc1234")
+	test("0.0.0-rc1", 1, "abc1234", "", "0.0.0-rc1.dev.1+gabc1234")
+	test("0.0.0-rc.1", 1, "abc1234", "", "0.0.0-rc.1.dev.1+gabc1234")
+	test("0.0.0-rc.1+foobar", 1, "abc1234", "", "0.0.0-rc.1.dev.1+gabc1234")
+	test("v0.0.0-rc.1+foobar", 1, "abc1234", "", "v0.0.0-rc.1.dev.1+gabc1234")
+
+	test("", 1, "abc1234", "0.0.0", "0.0.0-dev.1+gabc1234")
+	test("", 1, "abc1234", "v0.0.0", "v0.0.0-dev.1+gabc1234")
+	_, err := GenerateVersion("", 1, "abc1234", "")
+	assert.Error(err)
 }
 
 func TestRun(t *testing.T) {
 	assert := assert.New(t)
 	dir, _ := ioutil.TempDir("", "example")
-	_, err := Run(dir)
+	_, err := Run(dir, "")
 	assert.Error(err)
 
 	repo, _ := git.PlainInit(dir, false)
 	worktree, _ := repo.Worktree()
-	_, err = Run(dir)
+	_, err = Run(dir, "")
 	assert.Error(err)
 
 	commit1, _ := worktree.Commit("first", &git.CommitOptions{})
 	repo.CreateTag("invalid", commit1, nil)
-	_, err = Run(dir)
+	_, err = Run(dir, "")
 	assert.Error(err)
 
 	commit2, _ := worktree.Commit("first", &git.CommitOptions{})
 	repo.CreateTag("v1.0.0", commit2, nil)
 
 	commit3, _ := worktree.Commit("second", &git.CommitOptions{})
-	result, err := Run(dir)
+	result, err := Run(dir, "")
 	assert.NoError(err)
 	assert.Equal("v1.0.1-dev.1+g"+commit3.String()[0:7], *result)
 }