Stamp the tag or short commit in a plain docker build (closes #211)

A plain `docker build .` stamped `dev`: `.dockerignore` left out `.git`
and the Dockerfile defaulted VERSION to `dev`. `.dockerignore` now
sends `.git` without `.git/config`. Given no build arguments, the
builder stamps `git describe --tags --always` and the commit and date
from git, and fails if `.git` is present but yields no version. The
empty CHECK_EPOCH refusal is gone so the plain build succeeds.
`script/version` now prints `git describe --tags --always --dirty`, so
make, the scripts and a plain build agree. `vaultik version` treats
the short commit, tag-N-gHASH forms and any version ending in `-dirty`
as development builds, so they keep the development-build notice.

Model: opus-5-5

internal/globals/globals_test.go

@@ -34,10 +34,11 @@ func TestGlobalsNew(t *testing.T) {
 }
 
 // TestIsDevVersion covers the boundary that matters: everything
-// script/version and goreleaser's snapshot template can emit for an
-// untagged build must be recognised as a development build, and a real
-// tag must not be. A plain equality check against "dev" used to decide
-// this, which classified every commit-stamped dev build as a release.
+// script/version, a plain docker build and goreleaser's snapshot
+// template can emit for an untagged build must be recognised as a
+// development build, and a real tag must not be. A plain equality check
+// against "dev" used to decide this, which classified every
+// commit-stamped dev build as a release.
 func TestIsDevVersion(t *testing.T) {
 	t.Parallel()
 
@@ -49,8 +50,17 @@ func TestIsDevVersion(t *testing.T) {
 		{"dev", true},
 		{"dev-b6e4a218a39e", true},
 		{"dev-b6e4a218a39e-dirty", true},
-		// What a tagged build produces (script/version strips the
-		// leading "v", matching goreleaser's .Version).
+		// What `git describe --tags --always --dirty` produces with no
+		// tag reachable, and on a commit after a tag.
+		{"877eb2f", true},
+		{"877eb2f-dirty", true},
+		{"v1.0.0-3-g877eb2f", true},
+		{"v1.0.0-3-g877eb2f-dirty", true},
+		{"1.0.0-rc.1-12-g877eb2f", true},
+		// A tagged commit with uncommitted changes is not that tag.
+		{"v1.0.0-dirty", true},
+		// What a tagged build produces (goreleaser's .Version strips
+		// the leading "v"; script/version keeps it).
 		{"1.0.0", false},
 		{"0.1.0", false},
 		{"1.0.0-rc.1", false},