ci: discover the backends to substitute rather than listing them

openkal-musl names a backend per target --- linux, macos, windows and opensbi,
each conditional --- and every one of their versions moves with a change that
spans these repositories. Each left unsubstituted fails the same way, one link
further down:

    E_NOT_FOUND: package 'openkal-linux@0.6.0'      (the host build)
    E_NOT_FOUND: package 'openkal-opensbi@0.2.0'    (the bare-metal one)

I named the first and the second appeared. The commit that named the first said
"a chain is substituted correctly only when it is followed to its end", and then
followed it by hand to one entry short of the end, which is the ordinary outcome
of a list written from memory.

The set is now read out of the manifest, so it cannot fall behind what that
manifest declares.

⭐ AND THE LAST CHECK IS THE ONE THAT WOULD HAVE CAUGHT BOTH: after every
substitution, nothing anywhere in the graph may still name a version. That is a
property of the whole graph rather than of the entries someone remembered, and it
fails at the substitution rather than at a resolver error further on, where the
message names a package instead of naming the omission.

Author: speak-agent

.github/workflows/ci.yml

@@ -156,36 +156,52 @@ jobs:
             git -C .spec checkout --quiet "origin/$branch"
           fi
 
-          # ⚠️ THE WHOLE CHAIN, NOT THE FIRST TWO LINKS. openkal-musl names a
-          # BACKEND as well as the specification, and that backend's version
-          # moves with the same change:
+          # ⚠️ EVERY BACKEND THE C LIBRARY NAMES, DISCOVERED RATHER THAN LISTED.
           #
-          #     E_NOT_FOUND: package 'openkal-linux@0.6.0' not found
+          # openkal-musl names a backend per target: linux, macos, windows and
+          # opensbi, each conditional. Their versions all move with a change that
+          # spans these repositories, so each one left unsubstituted fails the
+          # same way, one link further down:
           #
-          # Substituting two of the three left the third naming a version the
-          # index does not have yet, which is the same failure one link further
-          # down. Every dependency that moves with this change is substituted.
-          git clone --quiet https://github.com/mcpplibs/openkal-linux.git .impl
-          if git -C .impl rev-parse --verify --quiet "origin/$branch" > /dev/null; then
-            git -C .impl checkout --quiet "origin/$branch"
-          fi
+          #     E_NOT_FOUND: package 'openkal-linux@0.6.0'   (the host build)
+          #     E_NOT_FOUND: package 'openkal-opensbi@0.2.0' (the bare-metal one)
+          #
+          # I fixed the first by naming it, and the second appeared. A list
+          # written by hand is a list that is one entry short, so the set is read
+          # out of the manifest instead.
+          for backend in $(grep -oE '^openkal-[a-z]+ = \{ version' .musl/mcpp.toml | cut -d' ' -f1); do
+            git clone --quiet "https://github.com/mcpplibs/$backend.git" ".$backend"
+            if git -C ".$backend" rev-parse --verify --quiet "origin/$branch" > /dev/null; then
+              git -C ".$backend" checkout --quiet "origin/$branch"
+            fi
+            here="$(cd ".$backend" && pwd)"
+            # The backend reaches the specification too, and by whatever form its
+            # own manifest uses.
+            sed -i -E "s|^openkal = .*$|openkal = { path = \"$(cd .spec && pwd)\" }|" ".$backend/mcpp.toml"
+            sed -i -E "s|^$backend = \\{ version = \"[^\"]*\"(.*)$|$backend = { path = \"$here\"\\1|" \
+                .musl/mcpp.toml
+            grep -q "path = \"$here\"" .musl/mcpp.toml \
+              || { echo "::error::$backend was not substituted"; exit 1; }
+            echo "  $backend -> working tree"
+          done
 
           spec="$(cd .spec && pwd)"
           musl="$(cd .musl && pwd)"
-          impl="$(cd .impl && pwd)"
-
-          sed -i -E "s|^openkal = .*$|openkal = { path = \"$spec\" }|" .impl/mcpp.toml
           sed -i -E "s|^openkal = .*$|openkal = { path = \"$spec\" }|" .musl/mcpp.toml
-          sed -i -E "s|^openkal-linux = \\{ version = \"[^\"]*\"(.*)$|openkal-linux = { path = \"$impl\"\\1|" \
-              .musl/mcpp.toml
           sed -i -E "s|^openkal-musl = .*$|openkal-musl = { path = \"$musl\" }|" mcpp.toml
 
-          for pair in "mcpp.toml:$musl" ".musl/mcpp.toml:$spec" ".musl/mcpp.toml:$impl" ".impl/mcpp.toml:$spec"; do
-            f="${pair%%:*}"; want="${pair##*:}"
-            grep -q "path = \"$want\"" "$f" \
-              || { echo "::error::a substitution matched nothing: $f should name $want"; exit 1; }
-          done
-          echo "the whole stack names working trees: runtime -> musl -> {openkal, openkal-linux}"
+          grep -q "path = \"$musl\"" mcpp.toml \
+            || { echo "::error::the C library substitution matched nothing"; exit 1; }
+          grep -q "path = \"$spec\"" .musl/mcpp.toml \
+            || { echo "::error::the specification substitution matched nothing"; exit 1; }
+
+          # ⚠️ THE LAST CHECK IS THE ONE THAT WOULD HAVE CAUGHT BOTH FAILURES:
+          # nothing anywhere in the substituted graph still names a version.
+          if grep -nE '^openkal[a-z-]* = (\"|\{ version)' .musl/mcpp.toml mcpp.toml; then
+            echo "::error::something in the graph still names a version rather than a tree"
+            exit 1
+          fi
+          echo "the whole stack names working trees, and nothing in it names a version"
 
       - name: The runtime builds
         run: mcpp build

.gitignore

@@ -17,3 +17,4 @@ mcpp.lock
 .musl/
 .spec/
 .impl/
+.openkal-*/