feat: share env files as encrypted links

S → f on a repo, an env file or a key in one copies a
lazysecrets://share link holding the env files, encrypted (age) with
a secret's value: whoever can read that secret can open it. The key is
share.key in the repo's .lazysecrets.yaml, else in the config, else
picked when sharing; on Azure the link pins its version. Opening one
says what it holds, decrypts when asked, and saves the files in the
clone of the repo (or a folder chosen), replacing existing ones only
when asked. lazysecrets share prints a link from the command line.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

internal/ref/ref.go

@@ -10,11 +10,15 @@
 //	lazysecrets://azure/<vault-host>[/<secrets|keys|certificates>[/<name>[/<version>]]]
 //	lazysecrets://databricks/<workspace-host>[/<scope>[/<key>]]
 //	lazysecrets://repo/<repo>[/<file>[/<key>]]
+//	lazysecrets://share/<sealed files>
 //
 // A repo is its git remote without scheme or .git
 // (git.kebcloud.no/keb/infra), the file its path in the repo and the key
 // its path in the file (db.password); slashes inside them are escaped.
 //
+// A share link carries files, encrypted (package share), instead of
+// naming something.
+//
 // Vault hosts always contain dots, so "subscriptions" can't be one.
 //
 // Every path segment is percent-encoded, so names may hold any character.
@@ -49,10 +53,19 @@ type Ref struct {
 	Type    provider.ObjectType
 	Name    string // object name; empty for a container link
 	Version string
+	// Share is a share link's sealed files, as in the link; the other
+	// fields are empty. Package share reads it.
+	Share string
 }
 
+// IsShare reports whether r is a share link.
+func (r Ref) IsShare() bool { return r.Share != "" }
+
 // IsSource reports whether r points at a subscription or workspace.
 func (r Ref) IsSource() bool {
+	if r.IsShare() {
+		return false
+	}
 	if r.Kind != provider.KindAzure {
 		return r.Scope == ""
 	}
@@ -60,7 +73,7 @@ func (r Ref) IsSource() bool {
 }
 
 // IsContainer reports whether r points at a vault or scope.
-func (r Ref) IsContainer() bool { return r.Name == "" && !r.IsSource() }
+func (r Ref) IsContainer() bool { return r.Name == "" && !r.IsSource() && !r.IsShare() }
 
 // ContainerName is the vault name (from its host) or the scope.
 func (r Ref) ContainerName() string {
@@ -111,6 +124,9 @@ func (r Ref) IdentifierURL() string {
 
 // String is the lazysecrets:// link.
 func (r Ref) String() string {
+	if r.IsShare() {
+		return Scheme + "://share/" + r.Share
+	}
 	if r.Kind == provider.KindAzure && r.Subscription != "" {
 		return Scheme + "://azure/subscriptions/" + url.PathEscape(r.Subscription)
 	}
@@ -208,6 +224,8 @@ var (
 	portalVault = regexp.MustCompile(`(?i)/providers/Microsoft\.KeyVault/vaults/([A-Za-z0-9-]+)`)
 	// …/asset/Microsoft_Azure_KeyVault/<Secret|Key|Certificate>/<identifier URL>
 	portalAsset = regexp.MustCompile(`(?i)/asset/Microsoft_Azure_KeyVault/[A-Za-z]+/(https://\S+)$`)
+	// a share link's sealed files: unpadded base64url
+	sealed = regexp.MustCompile(`^[A-Za-z0-9_-]{16,}$`)
 )
 
 // Parse reads any supported reference.
@@ -238,6 +256,12 @@ func parseLink(s string) (Ref, error) {
 	if err != nil {
 		return Ref{}, err
 	}
+	if strings.EqualFold(u.Host, "share") {
+		if len(segs) != 1 || !sealed.MatchString(segs[0]) {
+			return Ref{}, errors.New("share link is cut short or garbled: copy all of it")
+		}
+		return Ref{Share: segs[0]}, nil
+	}
 	var r Ref
 	if len(segs) == 0 || segs[0] == "" {
 		return Ref{}, errors.New("link has no vault or workspace")