Send .git without its config; correct shallow-clone and version comments

.dockerignore lists .git/config, which holds the clone's remote URL and
any credential in it; the build stage is the final image, so it would
otherwise ship. git describe does not need it. The build-context test
asserts the entry, and the README says the image carries .git without
its config.

The README now says a shallow clone stamps a tag only when the cloned
commit itself carries one, and otherwise the short commit. The comment in
src/index.ts says a build reports the version script/build stamps into
dist/package.json, and package.json's own version only from source.

Model: opus-5-5

.dockerignore

@@ -3,7 +3,10 @@
 # and dropping it would change what the lint phase's prettier check sees.
 #
 # .git is deliberately NOT excluded: the build derives the version it stamps
-# from it (script/version).
+# from it (script/version). It is sent without its config, which holds the
+# clone's remote URL and any credential in it, and which the build stage, the
+# final image, would otherwise carry. git describe does not need it.
+.git/config
 
 # OS
 .DS_Store

README.md

@@ -195,13 +195,15 @@ The build fails if the checkout has `.git` and the version still comes out
 empty, `dev` or `unknown`: such a build could not be traced back to its commit.
 
 `.dockerignore` therefore does not leave out `.git`, so any `docker build .` of
-a clone stamps the commit it was built from; a shallow clone of one branch has
-no tags and stamps the short commit. `script/docker` (and so `make docker`) and
-`script/cibuild` pass the version they resolve on the host, with `--dirty`, as
-the build arg, which takes precedence. The image's
-`org.opencontainers.image.version` label carries that build arg only, so a build
-given none leaves it empty. `make build-bin` bundles the built `dist/`, so the
-single binary reports the stamped version too.
+a clone stamps the commit it was built from; a shallow clone stamps a tag only
+when the cloned commit itself carries one, and otherwise the short commit. It
+leaves out `.git/config`, which holds the clone's remote URL and any credential
+in it, so the image carries `.git` without its config; `git describe` does not
+need that file. `script/docker` (and so `make docker`) and `script/cibuild` pass
+the version they resolve on the host, with `--dirty`, as the build arg, which
+takes precedence. The image's `org.opencontainers.image.version` label carries
+that build arg only, so a build given none leaves it empty. `make build-bin`
+bundles the built `dist/`, so the single binary reports the stamped version too.
 
 ## Rationale
 

src/index.ts

@@ -1,5 +1,7 @@
-// package.json is the one place the version is written. tsc copies it to
-// dist/package.json, so this path resolves from source and from dist/src/.
+// A build reports the version script/build stamps into dist/package.json;
+// package.json's own version is reported only when running from source. tsc
+// copies package.json to dist/package.json, so this path resolves from source
+// and from dist/src/.
 import pkg from "../package.json" with { type: "json" };
 
 export const VERSION: string = pkg.version;

test/packaging/build-context.test.ts

@@ -54,6 +54,12 @@ describe(".dockerignore", () => {
         expect(dockerignore).not.toContain(".git/");
     });
 
+    // The build stage is the final image, so a .git/config sent in would
+    // ship the clone's remote URL and any credential in it.
+    it("sends .git without its config", () => {
+        expect(dockerignore).toContain(".git/config");
+    });
+
     // BuildKit lets a `Dockerfile.dockerignore` shadow the root one; such a
     // file would silently give the build a different, unreviewed context —
     // and eslint's flat config does not ignore dot-directories, so a stray