Correct the phase-build comments in script/lint and script/test (closes #141)

The comments said a phase that is not the last stage is built only when
--target names it. The canonical Dockerfile's last stage copies from both
phases, so a plain build builds them too. The comments now say what
--target does in every repository: it builds that phase and the stages
it depends on, nothing else. The headers no longer say each script
builds its phase alone, which is false wherever the phase depends on
another stage.

Model: opus-5-5

.gitattributes

@@ -1,7 +1,2 @@
-# Every PR adds an entry at the top of TODO.md's Completed Steps; union keeps
-# both sides instead of conflicting. Git never reports a conflict here: read
-# the merged entries after every merge or rebase.
-TODO.md merge=union
-
 # yarn's release file is one opaque file in diffs and merges.
 .yarn/releases/** binary

TODO.md

@@ -2,7 +2,7 @@
 
 - branch (from `main`)
 - do the work in Next Step
-- move Next Step to the top of Completed Steps
+- delete Next Step from `TODO.md`
 - move the top item of Future Steps into Next Step
 - commit (`TODO.md` changes in the same commit as the work)
 - merge to `main` if the branch is not protected, otherwise open a PR

script/install-precommit

@@ -8,8 +8,8 @@ ROOT="$(cd "$(dirname "$0")/.." && pwd -P)"
 main() {
     cd "$ROOT"
     hook=".git/hooks/pre-commit"
-    printf '#!/bin/sh\nset -e\nscript/precommit\n' > .git/hooks/pre-commit
-    chmod +x .git/hooks/pre-commit
+    printf '#!/bin/sh\nset -e\nscript/precommit\n' > "$hook"
+    chmod +x "$hook"
     echo "pre-commit hook installed: runs script/precommit"
 }
 

script/lint

@@ -1,11 +1,11 @@
 #!/bin/sh
 # script/lint: run the linter. Linting is a phase of the Dockerfile and
-# this builds that phase alone; the linter is never installed or run on
+# this builds that phase; the linter is never installed or run on
 # a developer host, where a shared result cache and a host-global lock
 # make its answer untrustworthy.
 #
-# The phase is not the last stage in the file, so it is built only when
-# --target names it. A new CACHEBUST value reruns every RUN step after
+# --target builds the lint phase and the stages it depends on, nothing
+# else. A new CACHEBUST value reruns every RUN step after
 # the ARG CACHEBUST line, since a cached lint layer is a lint that did
 # not run; unlike --no-cache, it keeps the layers above that line and
 # the cache mounts. This relies on every stage of the Dockerfile

script/test

@@ -1,8 +1,8 @@
 #!/bin/sh
 # script/test: run the test suite. Testing is a phase of the Dockerfile
-# and this builds that phase alone, on the same terms as script/lint:
-# --target because a phase that is not the last stage is built only when
-# named, and a new CACHEBUST value because a cached test layer is a test
+# and this builds that phase, on the same terms as script/lint:
+# --target so that only the test phase and the stages it depends on are
+# built, and a new CACHEBUST value because a cached test layer is a test
 # that did not run; unlike --no-cache, it keeps the layers above the ARG
 # CACHEBUST line and the cache mounts. This relies on every stage of the
 # Dockerfile declaring ARG CACHEBUST before every step that lints, tests