Introducing changelog generation tool

.gitignore

@@ -0,0 +1 @@
+go.work*

libs/git/cmd.go

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+/*
+Copyright 2024 Gravitational, Inc.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+	http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package git
+
+import (
+	"bytes"
+	"os/exec"
+	"strings"
+
+	"github.com/gravitational/trace"
+)
+
+// IsAvailable returns status of git
+func IsAvailable() error {
+	_, err := exec.LookPath("git")
+	return err
+}
+
+// RunCmd runs git and returns output (stdout/stderr, depends on the cmd result) and error
+func (r *Repo) RunCmd(args ...string) (string, error) {
+	var stdout bytes.Buffer
+	var stderr bytes.Buffer
+
+	cmd := exec.Command("git", args...)
+	cmd.Stdout = &stdout
+	cmd.Stderr = &stderr
+	cmd.Dir = r.dir
+
+	err := cmd.Run()
+
+	if err != nil {
+		return strings.TrimSpace(stderr.String()), trace.Wrap(err)
+	}
+
+	return strings.TrimSpace(stdout.String()), nil
+}

libs/git/git.go

@@ -0,0 +1,99 @@
+/*
+Copyright 2024 Gravitational, Inc.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+	http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package git
+
+import (
+	"fmt"
+
+	go_git "github.com/go-git/go-git/v5"
+	"github.com/go-git/go-git/v5/plumbing"
+	"github.com/go-git/go-git/v5/plumbing/object"
+	"github.com/gravitational/trace"
+)
+
+// Repo provides a collection of functions to query and modify a single git repository.
+// Wrapper around the go-git library that also includes methods to execute git commands
+// on the system for missing compatability.
+type Repo struct {
+	dir        string
+	Repository *go_git.Repository
+}
+
+// NewRepoFromDirectory initializes [Repo] from a directory.
+func NewRepoFromDirectory(dir string) (*Repo, error) {
+	inner, err := go_git.PlainOpen(dir)
+	if err != nil {
+		return &Repo{}, trace.Wrap(err)
+	}
+
+	return &Repo{
+		dir:        dir,
+		Repository: inner,
+	}, nil
+}
+
+// GetCommitForTag attempts to get the resolved commit for a given tag.
+func (r *Repo) GetCommitForTag(tag string) (*object.Commit, error) {
+	t, err := r.Repository.Tag(tag)
+	if err != nil {
+		return &object.Commit{}, trace.Wrap(err, fmt.Sprintf("tag %q not found, use a valid git tag", tag))
+	}
+	return r.Repository.CommitObject(t.Hash())
+}
+
+// GetCommitForHead attempts to get the resolved commit for head.
+func (r *Repo) GetCommitForHead() (*object.Commit, error) {
+	ref, err := r.Repository.Reference(plumbing.HEAD, false)
+	if err != nil {
+		return &object.Commit{}, trace.Wrap(err, "can't get latest reference for ent")
+	}
+	return r.Repository.CommitObject(ref.Hash())
+}
+
+// GetBranchForHead attempts to get the resolved branch of HEAD.
+func (r *Repo) GetBranchNameForHead() (string, error) {
+	// symbolic-ref HEAD
+	ref, err := r.Repository.Reference(plumbing.HEAD, true)
+	if err != nil {
+		return "", trace.Wrap(err, "not on a branch")
+	}
+
+	if !ref.Name().IsBranch() {
+		return "", trace.BadParameter("not on a branch: %s", ref)
+	}
+	return ref.Name().String(), nil
+}
+
+// GetParentReleaseBranch will attempt to find a parent branch for HEAD.
+// This will also work if HEAD has branched from an earlier commit in a release branch e.g.
+//
+//	 o---o---HEAD
+//	/---o---o---branch/v16
+func (r *Repo) GetParentReleaseBranch() (string, error) {
+	forkPointRef, err := r.RunCmd("merge-base", "--fork-point", "HEAD")
+	if err != nil {
+		return "", trace.Wrap(err)
+	}
+	fbranch, err := r.RunCmd("branch", "--list", "branch/v*", "--contains", forkPointRef, "--format", "%(refname:short)")
+	if err != nil {
+		return "", trace.Wrap(err)
+	}
+	if fbranch == "" { // stdout is empty indicating the search failed
+		return "", trace.Errorf("could not find a valid root branch")
+	}
+	return fbranch, nil
+}

libs/git/go.mod

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+module github.com/gravitational/shared-workflows/libs/git
+
+go 1.22.4
+
+require (
+	github.com/go-git/go-git/v5 v5.12.0
+	github.com/gravitational/trace v1.3.1
+)
+
+require (
+	dario.cat/mergo v1.0.0 // indirect
+	github.com/Microsoft/go-winio v0.6.1 // indirect
+	github.com/ProtonMail/go-crypto v1.0.0 // indirect
+	github.com/cloudflare/circl v1.3.7 // indirect
+	github.com/cyphar/filepath-securejoin v0.2.4 // indirect
+	github.com/emirpasic/gods v1.18.1 // indirect
+	github.com/go-git/gcfg v1.5.1-0.20230307220236-3a3c6141e376 // indirect
+	github.com/go-git/go-billy/v5 v5.5.0 // indirect
+	github.com/golang/groupcache v0.0.0-20210331224755-41bb18bfe9da // indirect
+	github.com/jbenet/go-context v0.0.0-20150711004518-d14ea06fba99 // indirect
+	github.com/jonboulle/clockwork v0.4.0 // indirect
+	github.com/kevinburke/ssh_config v1.2.0 // indirect
+	github.com/pjbgf/sha1cd v0.3.0 // indirect
+	github.com/sergi/go-diff v1.3.2-0.20230802210424-5b0b94c5c0d3 // indirect
+	github.com/sirupsen/logrus v1.9.3 // indirect
+	github.com/skeema/knownhosts v1.2.2 // indirect
+	github.com/xanzy/ssh-agent v0.3.3 // indirect
+	golang.org/x/crypto v0.21.0 // indirect
+	golang.org/x/mod v0.13.0 // indirect
+	golang.org/x/net v0.22.0 // indirect
+	golang.org/x/sys v0.19.0 // indirect
+	golang.org/x/term v0.18.0 // indirect
+	golang.org/x/tools v0.14.0 // indirect
+	gopkg.in/warnings.v0 v0.1.2 // indirect
+)