Add build-nix.sh wrapper

README.md

@@ -149,14 +149,15 @@ snapshots.
 To run a similar build locally simply download a binary distribution from a
 `x86_64-fedora27-linux` CI job and run:
 ```
-$ nix build -f scripts/build-all.nix --keep-going testedPackages \
-    --arg bindistTarball ./ghc-x86_64-fedora27-linux.tar.xz \
-    --arg extraHcOpts \"-dcore-lint\"
+$ export GHC_TARBALL=./ghc-x86_64-fedora27-linux.tar.xz
+  # for extra correctness assurance...
+$ export EXTRA_HC_OPTS=-dcore-lint
+$ scripts/build-nix.sh
 ```
 This will build the set of packages defined by the `testedPackages` list in
 `scripts/build-all.nix`.
 
-After building `testedPackages` (allowing for failures) the CI job runs
+After building `testedPackages` (allowing for failures) the script job runs
 `scripts/summarize.py`, which produces a few artifacts:
 
  * a JSON summary (`summary.json`) which includes the full dependency graph as
@@ -165,10 +166,10 @@ After building `testedPackages` (allowing for failures) the CI job runs
    success. This can be rendered with `scripts/render-graph.sh`.
  * a directory (`./logs`) of build logs
 
-You can run `scripts/summarize.py` locally with
+Note that `build-nix.sh` can also be used to build packages not included in
+`testedPackages`:
 ```
-$ export GHC_TARBALL=./ghc-x86_64-fedora27-linux.tar.xz
-$ python3 scripts/summarize.py
+$ scripts/build-nix.sh pandoc
 ```
 
 ### Hackage repository

scripts/build-nix.sh

+#!/bin/sh
+
+# A convenient wrapper for build-all.nix.
+
+if [ -z "$GHC_TARBALL" ]; then
+  echo '$GHC_TARBALL is not set; please set it.'
+  exit 1
+fi
+
+targets=$@
+if [ -z "$targets" ]; then
+  targets=testedPackages
+fi
+
+echo "Building $targets with GHC options \"$EXTRA_HC_OPTS\"..."
+
+nix build -f scripts/build-all.nix --keep-going testedPackages \
+    --arg bindistTarball $GHC_TARBALL
+    --arg extraHcOpts \"$EXTRA_HC_OPTS\"
+
+echo "Build finished. Running summarize..."
+python3 scripts/summarize.py
+
+echo
+echo "Build finished. I produced the following:"
+echo " * summary.json: a summary of the build"
+echo " * summary.dot:  the dependency graph of packages I built"
+echo " * logs/*:       the build logs"
+echo