CHANGELOG.md

+# [1.0.0-alpha.5](https://git.gitlab.arm.com/bazel/git/compare/v1.0.0-alpha.4...v1.0.0-alpha.5) (2024-04-15)
+
+### Features
+
+- add `bazel-git show` command ([6b8f167](https://git.gitlab.arm.com/bazel/git/commit/6b8f16750751ee09984029842883151c39848f3c))
+- add `ls-tree` command ([19227f5](https://git.gitlab.arm.com/bazel/git/commit/19227f555e7c7717f1f07a4dd6368fbe9f7897f3))
+- **cat-file:** support existence of files ([1aa84f8](https://git.gitlab.arm.com/bazel/git/commit/1aa84f825e03d1e10d576576a6c3a72ee5566507))
+
 # [1.0.0-alpha.4](https://git.gitlab.arm.com/bazel/git/compare/v1.0.0-alpha.3...v1.0.0-alpha.4) (2024-04-11)
 
 ### Bug Fixes

MODULE.bazel

 module(
     name = "bazel-git",
-    version = "1.0.0-alpha.4",
+    version = "1.0.0-alpha.5",
     bazel_compatibility = [
         ">=7.0.0",
     ],
@@ -12,7 +12,7 @@ bazel_dep(name = "rules_coreutils", version = "1.0.0-alpha.8")
 bazel_dep(name = "rules_go", version = "0.46.0")
 bazel_dep(name = "rules_diff", version = "1.0.0-alpha.3")
 bazel_dep(name = "hermetic_cc_toolchain", version = "3.0.0")
-bazel_dep(name = "gazelle", version = "0.35.0")
+bazel_dep(name = "gazelle", version = "0.36.0")
 bazel_dep(name = "circl", version = "1.3.3")
 
 # Need https://github.com/bazelbuild/rules_go/pull/3872 to be hermetic

cmd/bazel-git/BUILD.bazel

-load(":pure.bzl", "COUPLETS")
 load("@rules_go//go:def.bzl", "go_binary", "go_library")
+load(":pure.bzl", "COUPLETS")
 
 go_library(
     name = "bazel-git_lib",
@@ -11,7 +11,9 @@ go_library(
         "fetch.go",
         "init.go",
         "ls_remote.go",
+        "ls_tree.go",
         "main.go",
+        "show.go",
     ],
     importpath = "gitlab.arm.com/bazel/git/v1/cmd/bazel-git",
     visibility = ["//visibility:private"],
@@ -22,9 +24,11 @@ go_library(
         "@com_github_go_git_go_git_v5//config:go_default_library",
         "@com_github_go_git_go_git_v5//plumbing:go_default_library",
         "@com_github_go_git_go_git_v5//plumbing/cache:go_default_library",
+        "@com_github_go_git_go_git_v5//plumbing/object:go_default_library",
         "@com_github_go_git_go_git_v5//plumbing/protocol/packp/sideband:go_default_library",
         "@com_github_go_git_go_git_v5//storage/filesystem:go_default_library",
         "@com_github_go_git_go_git_v5//storage/memory:go_default_library",
+        "@com_github_go_git_go_git_v5//utils/ioutil:go_default_library",
         "@com_github_jessevdk_go_flags//:go_default_library",
         "@com_github_kevinburke_ssh_config//:go_default_library",
         "@com_github_mattn_go_isatty//:go_default_library",

cmd/bazel-git/cat_file.go

@@ -3,15 +3,17 @@ package main
 import (
 	"errors"
 	"log/slog"
+	"strings"
 
 	"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/jessevdk/go-flags"
 )
 
 type CatFileCommand struct {
-	ExitCode bool `short:"e" description:"Exit with zero status if <object> exists and is a valid object. If <object> is of an invalid format, exit with non-zero status and emit an error on stderr." required:"yes"`
-	Args     struct {
+	Exists bool `short:"e" description:"Exit with zero status if <object> exists and is a valid object. If <object> is of an invalid format, exit with non-zero status and emit an error on stderr." required:"yes"`
+	Args   struct {
 		Revision plumbing.Revision `positional-arg-name:"<object>" description:"The object to check for existence."`
 	} `positional-args:"yes" required:"yes"`
 }
@@ -34,7 +36,7 @@ func (x *CatFileCommand) Execute(rest []string) error {
 
 	log.Debug("resolve")
 	hash, err := repo.ResolveRevision(x.Args.Revision)
-	if x.ExitCode && err == plumbing.ErrReferenceNotFound {
+	if x.Exists && err == plumbing.ErrReferenceNotFound {
 		// TODO: remove the message
 		return NewExitCodeError(1, "Not found")
 	}
@@ -44,7 +46,38 @@ func (x *CatFileCommand) Execute(rest []string) error {
 	}
 	log.Debug("resolved", "hash", hash)
 
-	if x.ExitCode {
+	if x.Exists && strings.Contains(x.Args.Revision.String(), ":") {
+		log.Debug("commit")
+		commit, err := repo.CommitObject(*hash)
+		if err != nil {
+			log.Error("commit", "err", err)
+			return err
+		}
+
+		log.Debug("tree")
+		tree, err := commit.Tree()
+		if err != nil {
+			log.Error("tree", "err", err)
+			return err
+		}
+
+		filepath := strings.SplitN(x.Args.Revision.String(), ":", 2)[1]
+
+		log.Debug("file", "filepath", filepath)
+		_, err = tree.File(filepath)
+		if err == object.ErrFileNotFound {
+			// TODO: remove the message
+			return NewExitCodeError(1, "Not found")
+		}
+		if err != nil {
+			log.Error("tree", "err", err)
+			return err
+		}
+
+		return nil
+	}
+
+	if x.Exists {
 		return nil
 	}
 

cmd/bazel-git/ls_tree.go

+package main
+
+import (
+	"encoding/hex"
+	"fmt"
+	"log/slog"
+	"regexp"
+	"strings"
+
+	"github.com/go-git/go-git/v5"
+	"github.com/go-git/go-git/v5/plumbing"
+	"github.com/jessevdk/go-flags"
+)
+
+const gitLink = 0160000
+
+type LsTreeCommand struct {
+	Format string `long:"format" value-name:"<format>" description:"A string that interpolates %(fieldname) from the result being shown." default:"%(objectmode) %(objecttype) %(objectname)%x09%(path)"`
+	Args   struct {
+		Revision plumbing.Revision `positional-arg-name:"<tree-ish>" description:"Identifier or a tree-ish."`
+		Paths    []string          `positional-arg-name:"<path>" description:"The paths to list."`
+	} `positional-args:"yes" required:"yes"`
+}
+
+var lsTreeCommand LsTreeCommand
+
+func (x *LsTreeCommand) Execute(rest []string) error {
+	if len(rest) != 0 {
+		return &flags.Error{flags.ErrDuplicatedFlag, "invalid number of positional arguments"}
+	}
+
+	log := slog.With("cmd", "ls-tree", "object", x.Args.Revision, "path", x.Args.Paths)
+
+	log.Debug("open", "git-dir", options.GitDir)
+	repo, err := git.PlainOpen(options.GitDir)
+	if err != nil {
+		log.Error("open", "err", err)
+		return err
+	}
+
+	log.Debug("resolve")
+	hash, err := repo.ResolveRevision(x.Args.Revision)
+	if err != nil {
+		log.Error("resolve", "err", err)
+		return err
+	}
+	log.Debug("resolved", "hash", hash)
+
+	log.Debug("commit")
+	commit, err := repo.CommitObject(*hash)
+	if err != nil {
+		log.Error("commit", "err", err)
+		return err
+	}
+
+	log.Debug("tree")
+	tree, err := commit.Tree()
+	if err != nil {
+		log.Error("tree", "err", err)
+		return err
+	}
+
+	entries := tree.Entries
+	if 0 != len(x.Args.Paths) {
+		entries = nil
+		for _, path := range x.Args.Paths {
+			log.Debug("find")
+			entry, err := tree.FindEntry(path)
+			if err != nil {
+				log.Error("find", "err", err)
+				return err
+			}
+			entry.Name = path
+			entries = append(entries, *entry)
+		}
+	}
+
+	re := regexp.MustCompile(`%(?:%|x[a-fA-F0-9]{2}|\((?:objectmode|objecttype|objectname|path)\))`)
+
+	for _, entry := range entries {
+		var kind string
+		if entry.Mode == gitLink {
+			kind = "commit"
+		} else {
+			object, err := repo.Object(plumbing.AnyObject, entry.Hash)
+			if err != nil {
+				return err
+			}
+			kind = object.Type().String()
+		}
+
+		replace := func(value string) string {
+			switch value {
+			case "%(objecttype)":
+				return kind
+			case "%(objectmode)":
+				return fmt.Sprintf("%06o", entry.Mode)
+			case "%(objectname)":
+				return entry.Hash.String()
+			case "%(path)":
+				return entry.Name
+			case "%%":
+				return "%"
+			}
+
+			if strings.HasPrefix(value, "%x") {
+				if bytes, err := hex.DecodeString(value[2:]); err == nil {
+					return string(bytes)
+				}
+			}
+
+			return value
+		}
+
+		line := re.ReplaceAllStringFunc(x.Format, replace)
+		fmt.Println(line)
+	}
+
+	return err
+}
+
+func init() {
+	parser.AddCommand("ls-tree",
+		"List the contents of a tree object.",
+		`Lists the contents of a given tree object, like what "/bin/ls -a" does in the current working directory.`,
+		&lsTreeCommand)
+}

cmd/bazel-git/show.go

+package main
+
+import (
+	"fmt"
+	"io"
+	"log/slog"
+	"os"
+	"strings"
+
+	"github.com/go-git/go-git/v5"
+	"github.com/go-git/go-git/v5/plumbing"
+	"github.com/go-git/go-git/v5/utils/ioutil"
+	"github.com/jessevdk/go-flags"
+)
+
+type ShowCommand struct {
+	Args struct {
+		Revision plumbing.Revision `positional-arg-name:"<object>" description:"The object to show."`
+	} `positional-args:"yes" required:"yes"`
+}
+
+var showCommand ShowCommand
+
+func (x *ShowCommand) Execute(rest []string) error {
+	if len(rest) != 0 {
+		return &flags.Error{flags.ErrDuplicatedFlag, "invalid number of positional arguments"}
+	}
+
+	log := slog.With("cmd", "show", "object", x.Args.Revision)
+
+	log.Debug("open", "git-dir", options.GitDir)
+	repo, err := git.PlainOpen(options.GitDir)
+	if err != nil {
+		log.Error("open", "err", err)
+		return err
+	}
+
+	log.Debug("resolve")
+	hash, err := repo.ResolveRevision(x.Args.Revision)
+	if err != nil {
+		log.Error("resolve", "err", err)
+		return err
+	}
+	log.Debug("resolved", "hash", hash)
+
+	if !strings.Contains(x.Args.Revision.String(), ":") {
+		return fmt.Errorf("Only blobs with filepaths are supported (`<commit>:<filepath>`) : %s", x.Args.Revision.String())
+	}
+
+	log.Debug("commit")
+	commit, err := repo.CommitObject(*hash)
+	if err != nil {
+		log.Error("commit", "err", err)
+		return err
+	}
+
+	log.Debug("tree")
+	tree, err := commit.Tree()
+	if err != nil {
+		log.Error("tree", "err", err)
+		return err
+	}
+
+	filepath := strings.SplitN(x.Args.Revision.String(), ":", 2)[1]
+
+	log.Debug("file", "filepath", filepath)
+	file, err := tree.File(filepath)
+	if err != nil {
+		log.Error("tree", "err", err)
+		return err
+	}
+
+	log.Debug("reader")
+	reader, err := file.Reader()
+	if err != nil {
+		log.Error("reader", "err", err)
+		return err
+	}
+	defer ioutil.CheckClose(reader, &err)
+
+	log.Debug("copy")
+	_, err = io.Copy(os.Stdout, reader)
+	if err != nil {
+		log.Error("copy", "err", err)
+		return err
+	}
+
+	return err
+}
+
+func init() {
+	parser.AddCommand("show",
+		"Show various types of objects.",
+		`Shows one or more objects (blobs, tree, tags and commits).
+
+ For commits it shows the log message and textual diff. It also presents the merge
+ commit in a special format as produced by 'git diff-tree --cc'.
+
+ For tags, it shows the tag message and the referenced objects.
+
+ For trees, it shows the names (equivalent to 'git ls-tree' with '--name-only').
+
+ For plain blobs, it shows the plain contents.`,
+		&showCommand)
+}