feat: use CI environment variables to figure out tag (#1327)

* fix(git): Use CI envronment variables to figure out tag

This patch detects CI environments and uses the available tag information when
collecting the git tag.

This resolves issues where one commit has multiple tags.

Closes #1163
Closes #1311

* Update www/content/release.md

Co-Authored-By: Carlos Alexandro Becker <caarlos0@users.noreply.github.com>

* Update www/content/release.md

Co-Authored-By: Carlos Alexandro Becker <caarlos0@users.noreply.github.com>

* Update www/content/build.md

Co-Authored-By: Carlos Alexandro Becker <caarlos0@users.noreply.github.com>

* Update www/content/release.md

Co-Authored-By: Carlos Alexandro Becker <caarlos0@users.noreply.github.com>

* feat(doc): Document git tag override in environment

Co-authored-by: Carlos Alexandro Becker <caarlos0@users.noreply.github.com>

internal/pipe/changelog/changelog.go

@@ -5,6 +5,7 @@ import (
 	"errors"
 	"fmt"
 	"io/ioutil"
+	"os"
 	"path/filepath"
 	"regexp"
 	"sort"
@@ -189,6 +190,10 @@ func gitLog(refs ...string) (string, error) {
 }
 
 func previous(tag string) (result string, err error) {
+	if tag := os.Getenv("GORELEASER_PREVIOUS_TAG"); tag != "" {
+		return tag, nil
+	}
+
 	result, err = git.Clean(git.Run("describe", "--tags", "--abbrev=0", fmt.Sprintf("tags/%s^", tag)))
 	if err != nil {
 		result, err = git.Clean(git.Run("rev-list", "--max-parents=0", "HEAD"))

internal/pipe/changelog/changelog_test.go

@@ -109,6 +109,30 @@ func TestChangelog(t *testing.T) {
 	require.NotEmpty(t, string(bts))
 }
 
+func TestChangelogPreviousTagEnv(t *testing.T) {
+	folder, back := testlib.Mktmp(t)
+	defer back()
+	testlib.GitInit(t)
+	testlib.GitCommit(t, "first")
+	testlib.GitTag(t, "v0.0.1")
+	testlib.GitCommit(t, "second")
+	testlib.GitTag(t, "v0.0.2")
+	testlib.GitCommit(t, "third")
+	testlib.GitTag(t, "v0.0.3")
+	var ctx = context.New(config.Project{
+		Dist:      folder,
+		Changelog: config.Changelog{Filters: config.Filters{}},
+	})
+	ctx.Git.CurrentTag = "v0.0.3"
+	require.NoError(t, os.Setenv("GORELEASER_PREVIOUS_TAG", "v0.0.1"))
+	require.NoError(t, Pipe{}.Run(ctx))
+	require.NoError(t, os.Setenv("GORELEASER_PREVIOUS_TAG", ""))
+	require.Contains(t, ctx.ReleaseNotes, "## Changelog")
+	require.NotContains(t, ctx.ReleaseNotes, "first")
+	require.Contains(t, ctx.ReleaseNotes, "second")
+	require.Contains(t, ctx.ReleaseNotes, "third")
+}
+
 func TestChangelogForGitlab(t *testing.T) {
 	folder, back := testlib.Mktmp(t)
 	defer back()

internal/pipe/git/git.go

@@ -1,14 +1,16 @@
 package git
 
 import (
+	"os"
 	"os/exec"
 	"strings"
 
 	"github.com/apex/log"
+	"github.com/pkg/errors"
+
 	"github.com/goreleaser/goreleaser/internal/git"
 	"github.com/goreleaser/goreleaser/internal/pipe"
 	"github.com/goreleaser/goreleaser/pkg/context"
-	"github.com/pkg/errors"
 )
 
 // Pipe that sets up git state
@@ -122,6 +124,10 @@ func getFullCommit() (string, error) {
 }
 
 func getTag() (string, error) {
+	if tag := os.Getenv("GORELEASER_CURRENT_TAG"); tag != "" {
+		return tag, nil
+	}
+
 	return git.Clean(git.Run("describe", "--tags", "--abbrev=0"))
 }
 

internal/pipe/git/git_test.go

@@ -6,10 +6,12 @@ import (
 	"path/filepath"
 	"testing"
 
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+
 	"github.com/goreleaser/goreleaser/internal/testlib"
 	"github.com/goreleaser/goreleaser/pkg/config"
 	"github.com/goreleaser/goreleaser/pkg/context"
-	"github.com/stretchr/testify/assert"
 )
 
 func TestDescription(t *testing.T) {
@@ -189,3 +191,41 @@ func TestGitNotInPath(t *testing.T) {
 	assert.NoError(t, os.Setenv("PATH", ""))
 	assert.EqualError(t, Pipe{}.Run(context.New(config.Project{})), ErrNoGit.Error())
 }
+
+func TestTagFromCI(t *testing.T) {
+	_, back := testlib.Mktmp(t)
+	defer back()
+	testlib.GitInit(t)
+	testlib.GitRemoteAdd(t, "git@github.com:foo/bar.git")
+	testlib.GitCommit(t, "commit1")
+	testlib.GitTag(t, "v0.0.1")
+	testlib.GitTag(t, "v0.0.2")
+
+	for _, tc := range []struct {
+		envs     map[string]string
+		expected string
+	}{
+		// It is not possible to concisely figure out the tag if a commit has more than one tags. Git always
+		// returns the tags in lexicographical order (ASC), which implies that we expect v0.0.1 here.
+		// More details: https://github.com/goreleaser/goreleaser/issues/1163
+		{expected: "v0.0.1"},
+		{
+			envs:     map[string]string{"GORELEASER_CURRENT_TAG": "v0.0.2"},
+			expected: "v0.0.2",
+		},
+	} {
+		for name, value := range tc.envs {
+			require.NoError(t, os.Setenv(name, value))
+		}
+
+		var ctx = &context.Context{
+			Config: config.Project{},
+		}
+		assert.NoError(t, Pipe{}.Run(ctx))
+		assert.Equal(t, tc.expected, ctx.Git.CurrentTag)
+
+		for name := range tc.envs {
+			require.NoError(t, os.Setenv(name, ""))
+		}
+	}
+}

www/content/build.md

@@ -149,3 +149,9 @@ GOVERSION=$(go version) goreleaser
  ```
 
  [hook]: /hooks
+
+## Define Build Tag
+
+GoReleaser uses `git describe` to get the build tag. You can set
+a different build tag using the environment variable `GORELEASER_CURRENT_TAG`.
+This is useful in scenarios where two tags point to the same commit.

www/content/environment.md

@@ -117,3 +117,7 @@ func main() {
 ```
 
 You can override this by changing the `ldflags` option in the `build` section.
+
+## Overriding Git Tags
+
+You can force the [build tag](/build#define-build-tag) and [previous changelog tag](/release#define-previous-tag) using environment variables. This is useful in cases where one git commit is referenced by multiple git tags.

www/content/release.md

@@ -137,6 +137,12 @@ changelog:
       - (?i)foo
 ```
 
+### Define Previous Tag
+
+GoReleaser uses `git describe` to get the previous tag used for generating the Changelog.
+You can set a different build tag using the environment variable `GORELEASER_PREVIOUS_TAG`.
+This is useful in scenarios where two tags point to the same commit.
+
 ## Custom release notes
 
 You can specify a file containing your custom release notes, and