feat(git): add explicit Blobless opt-in to BareCloneOptions and CloneOptions

pkg/controller/git/bare_repo.go

@@ -7,7 +7,6 @@ import (
 	"os"
 	"path/filepath"
 	"slices"
-	"strings"
 
 	libExec "github.com/akuity/kargo/pkg/exec"
 )
@@ -69,11 +68,12 @@ type BareCloneOptions struct {
 	// should be ignored when cloning the repository. The setting will be
 	// remembered for subsequent interactions with the remote repository.
 	InsecureSkipTLSVerify bool
-	// Filter specifies a partial clone filter (e.g., "blob:none"). When combined
-	// with sparse checkout, this avoids downloading blobs for directories that
-	// won't be checked out, significantly reducing clone time and disk usage for
-	// large repositories.
-	Filter string
+	// Blobless enables blobless cloning (--filter=blob:none). When set, the
+	// initial clone downloads all commits and trees but defers blob downloads
+	// until checkout. Combine with sparse checkout to minimise disk usage on
+	// large repositories. The server must support partial clones; if it does
+	// not, the clone will fail.
+	Blobless bool
 }
 
 // CloneBare produces a local, bare clone of the remote Git repository at the
@@ -117,14 +117,14 @@ func CloneBare(
 	return b, nil
 }
 
-func (b *bareRepo) clone(_ *BareCloneOptions) error {
+func (b *bareRepo) clone(opts *BareCloneOptions) error {
+	if opts == nil {
+		opts = &BareCloneOptions{}
+	}
 	args := []string{"clone", "--bare"}
-	// NOTE(hidde): Temporarily disabled until we figure out why this can result
-	// in "could not fetch <commit> from promisor remote" errors.
-	//
-	// if opts.Filter != "" {
-	//  	args = append(args, "--filter", opts.Filter)
-	// }
+	if opts.Blobless {
+		args = append(args, "--filter", "blob:none")
+	}
 	args = append(args, b.accessURL, b.dir)
 	cmd := b.buildGitCommand(args...)
 	cmd.Dir = b.homeDir // Override the cmd.Dir that's set by r.buildGitCommand()
@@ -133,7 +133,6 @@ func (b *bareRepo) clone(_ *BareCloneOptions) error {
 	}
 	return nil
 }
-
 type LoadBareRepoOptions struct {
 	Credentials *RepoCredentials
 }

pkg/controller/git/repo.go

@@ -45,16 +45,12 @@ type CloneOptions struct {
 	// Depth is the number of commits to fetch from the remote repository. If
 	// zero, all commits will be fetched. This option is ignored if Bare is true.
 	Depth uint
-	// Filter allows for partially cloning the repository by specifying a
-	// filter. When a filter is specified, the server will only send a
-	// subset of reachable objects according to a given object filter.
-	//
-	// For more information, see:
-	// - https://git-scm.com/docs/git-clone#Documentation/git-clone.txt-code--filtercodeemltfilter-specgtem
-	// - https://git-scm.com/docs/git-rev-list#Documentation/git-rev-list.txt---filterltfilter-specgt
-	// - https://github.blog/2020-12-21-get-up-to-speed-with-partial-clone-and-shallow-clone/
-	// - https://docs.gitlab.com/ee/topics/git/partial_clone.html
-	Filter string
+	// Blobless enables blobless cloning (--filter=blob:none). When set, the
+	// initial clone downloads all commits and trees but defers blob downloads
+	// until checkout. Combine with sparse checkout to minimise disk usage on
+	// large repositories. The server must support partial clones; if it does
+	// not, the clone will fail.
+	Blobless bool
 	// SingleBranch indicates whether the clone should be a single-branch clone.
 	// This option is ignored if Bare is true.
 	SingleBranch bool
@@ -119,12 +115,9 @@ func (r *repo) clone(opts *CloneOptions) error {
 	if opts.Depth > 0 {
 		args = append(args, "--depth", fmt.Sprint(opts.Depth))
 	}
-	// NOTE(hidde): Temporarily disabled until we figure out why this can result
-	// in "could not fetch <commit> from promisor remote" errors.
-	//
-	// if opts.Filter != "" {
-	//  	args = append(args, "--filter", opts.Filter)
-	// }
+	if opts.Blobless {
+		args = append(args, "--filter", "blob:none")
+	}
 	args = append(args, r.accessURL, r.dir)
 	cmd := r.buildGitCommand(args...)
 	cmd.Dir = r.homeDir // Override the cmd.Dir that's set by r.buildGitCommand()
@@ -133,7 +126,6 @@ func (r *repo) clone(opts *CloneOptions) error {
 	}
 	return nil
 }
-
 type LoadRepoOptions struct {
 	Credentials *RepoCredentials
 }

pkg/promotion/runner/builtin/git_cloner.go

@@ -41,6 +41,21 @@ type gitCloner struct {
 	schemaLoader    gojsonschema.JSONLoader
 }
 
+// gitUserFromEnv populates a git.User struct from environment variables.
+func gitUserFromEnv() git.User {
+	cfg := struct {
+		Name           string `envconfig:"GITCLIENT_NAME"`
+		Email          string `envconfig:"GITCLIENT_EMAIL"`
+		SigningKeyType string `envconfig:"GITCLIENT_SIGNING_KEY_TYPE"`
+		SigningKeyPath string `envconfig:"GITCLIENT_SIGNING_KEY_PATH"`
+	}{}
+	envconfig.MustProcess("", &cfg)
+	return git.User{
+		Name:           cfg.Name,
+		Email:          cfg.Email,
+		SigningKeyType: git.SigningKeyType(cfg.SigningKeyType),
+		SigningKeyPath: cfg.SigningKeyPath,
+	}
 // filterForCheckouts returns the clone filter to use based on checkout
 // configurations. Returns git.FilterBlobless if all checkouts specify sparse
 // patterns, returns empty string otherwise to avoid on-demand blob fetches for
@@ -148,7 +163,7 @@ func (g *gitCloner) run(
 		},
 		&git.BareCloneOptions{
 			BaseDir: stepCtx.WorkDir,
-			Filter:  filterForCheckouts(cfg.Checkout),
+			Blobless: cfg.Blobless,
 		},
 	)
 	if err != nil {

pkg/promotion/runner/builtin/schemas/git-clone-config.json

@@ -13,6 +13,10 @@
       "type": "boolean",
       "description": "Indicates whether to recursively clone submodules. Default is false. Note that any provided credentials must also be valid for the submodules."
     },
+    "blobless": {
+      "type": "boolean",
+      "description": "Indicates whether to perform a blobless (--filter=blob:none) clone. Default is false."
+    },
     "repoURL": {
       "type": "string",
       "description": "The URL of a remote Git repository to clone. Required. Deprecated: Support for SSH URLs (ssh:// and SCP-style git@host:path) is deprecated as of v1.10.0 and will be removed in v1.13.0. Use HTTPS URLs instead.",