Add brief inspect command and Artifact report

.gitignore

@@ -7,6 +7,7 @@
 *.dll
 *.so
 *.dylib
+bin/
 
 # Test binary, built with `go test -c`
 *.test

artifact.go

@@ -0,0 +1,32 @@
+package brief
+
+import "github.com/git-pkgs/brief/binary"
+
+// Artifact is the output of inspecting a distributed package archive or a
+// bare native object file.
+type Artifact struct {
+	Version string `json:"version"`
+	Path    string `json:"path"`
+
+	// Format is the physical container format as reported by
+	// git-pkgs/magic: "zip", "gzip", "tar", "elf", "mach-o", "pe".
+	// Packaging-level identity (wheel, gem, jar) is added by later
+	// container metadata parsing.
+	Format string `json:"format"`
+
+	// SHA256 is the hex-encoded digest of the raw input file.
+	SHA256 string `json:"sha256,omitempty"`
+
+	// Entries is the total number of regular-file entries walked when the
+	// input is an archive. Zero for bare native objects.
+	Entries int `json:"entries,omitempty"`
+
+	// NativeObjects lists every ELF, Mach-O, or PE object found: the input
+	// itself when it is a bare native object, or each such entry inside an
+	// archive.
+	NativeObjects []binary.Object `json:"native_objects,omitempty"`
+
+	// DurationMS is wall-clock milliseconds spent producing the report,
+	// excluding archive download time.
+	DurationMS float64 `json:"duration_ms"`
+}