Add update-dmd-rewrite.sh script

tools/update-dmd-rewrite.sh

@@ -0,0 +1,105 @@
+#!/usr/bin/env bash
+set -euxo pipefail
+
+# This script creates a fresh temporary clone of the DMD repo and rewrites
+# it (via `git filter-repo`) according to LDC requirements (removing
+# unnecessary files and transforming the directory structure).
+# Then it pushes new tags and updated master/stable branches (all prefixed
+# with `dmd-rewrite-`) to the LDC repo, i.e., the rewritten updates to
+# the DMD repo since the last successful script invocation.
+#
+# Afterwards, merging a new frontend+druntime is a matter of merging branch
+# `dmd-rewrite-stable` or some tag (`dmd-rewrite-v2.101.0`).
+
+initialize="${INITIALIZE:-0}" # set INITIALIZE=1 for the very first rewrite
+refs_prefix="dmd-rewrite-"
+
+temp_dir="$(mktemp -d)"
+cd "$temp_dir"
+
+# generate message-filters.txt file for replacing GitHub refs in commit messages
+echo 'regex:(^|\s|\()#(\d{2,})==>\1dlang/dmd!\2' > message-filters.txt
+
+# clone DMD monorepo
+git clone [email protected]:dlang/dmd.git dmd.tmp
+cd dmd.tmp
+
+# only for initialization:
+# merge LDC druntime patches (tag: first-merged-dmd-druntime-with-ldc-druntime-patches)
+if [[ "$initialize" == 1 ]]; then
+  git checkout -b ldc-tmp first-merged-dmd-druntime --no-track
+  git subtree pull --prefix druntime [email protected]:ldc-developers/druntime.git ldc-pre-monorepo -m "Merge LDC pre-monorepo druntime patches"
+  git tag first-merged-dmd-druntime-with-ldc-druntime-patches
+fi
+
+# extract a subset of the dmd monorepo (druntime source + tests + Makefiles, dmd source + tests + osmodel.mak)
+git filter-repo --force \
+  --path druntime/src --path druntime/test --path-glob 'druntime/*.mak' \
+  --path compiler/src/dmd --path compiler/test --path compiler/src/osmodel.mak \
+  --path src --path test # required to keep git history before upstream druntime-merge (and associated directory movals)
+# remove unused files
+git filter-repo --invert-paths \
+  --path-regex '(compiler/)?src/dmd/backend' \
+  --path-regex '(compiler/)?src/dmd/root/(env|response|strtold)\.d' \
+  --path-regex '(compiler/)?src/dmd/astbase\.d' \
+  --path-regex '(compiler/)?src/dmd/cpreprocess\.d' \
+  --path-regex '(compiler/)?src/dmd/dinifile\.d' \
+  --path-regex '(compiler/)?src/dmd/dmdparams\.d' \
+  --path-regex '(compiler/)?src/dmd/dmsc\.d' \
+  --path-regex '(compiler/)?src/dmd/eh\.d' \
+  --path-regex '(compiler/)?src/dmd/frontend\.d' \
+  --path-regex '(compiler/)?src/dmd/scan(elf|mach|mscoff|omf)\.d' \
+  --path-regex '(compiler/)?src/dmd/lib(|elf|mach|mscoff|omf)\.d' \
+  --path-regex '(compiler/)?src/dmd/link\.d' \
+  --path-regex '(compiler/)?src/dmd/(e|s)2ir\.d' \
+  --path-regex '(compiler/)?src/dmd/to(csym|ctype|cvdebug|dt|ir|obj)\.d' \
+  --path-regex '(compiler/)?src/dmd/iasm(|dmd)\.d' \
+  --path-regex '(compiler/)?src/dmd/(objc_)?glue\.d' \
+  --path-glob 'src/*.mak' # remaining Makefiles after moving dmd into compiler/
+git filter-repo \
+  `# move dirs/files` \
+  --path-rename druntime/:runtime/druntime/ \
+  --path-rename compiler/src/dmd/:dmd/ \
+  --path-rename compiler/test/:tests/dmd/ \
+  --path-rename compiler/src/osmodel.mak:dmd/osmodel.mak \
+  `# prefix tags` \
+  --tag-rename ":$refs_prefix" \
+  `# replace GitHub refs in commit messages` \
+  --replace-message ../message-filters.txt
+
+# create prefixed master/stable branches
+git branch --no-track "${refs_prefix}master" master
+git branch --no-track "${refs_prefix}stable" stable
+
+# add LDC repo as `ldc` remote
+git remote add ldc [email protected]:ldc-developers/ldc.git
+
+# check for newly added DMD source files
+if [[ "$initialize" != 1 ]]; then
+  git fetch ldc "${refs_prefix}master"
+  numFiles="$(git diff --name-only --diff-filter=A --relative=dmd "ldc/${refs_prefix}master..${refs_prefix}master" | wc -l)"
+  if [[ "$numFiles" != 0 ]]; then
+    set +x
+    echo "$numFiles newly added DMD source files in branch master:"
+    echo "----------"
+    git diff --name-only --diff-filter=A --relative=dmd "ldc/${refs_prefix}master..${refs_prefix}master"
+    echo "----------"
+    if [[ "${FORCE:-0}" == 1 ]]; then
+      echo "Adding these files due to env variable FORCE=1."
+    else
+      echo "Aborting due to these newly added files."
+      echo "Please check if they are of interest to LDC:"
+      echo "* If they aren't, have them removed via filter-repo in this script, then re-run the script."
+      echo "* If they are, re-run this script with env variable FORCE=1."
+      exit 1
+    fi
+    set -x
+  fi
+fi
+
+# push prefixed master/stable branches and tags
+# TODO: remove dry-run
+git push --dry-run --tags ldc "${refs_prefix}master" "${refs_prefix}stable"
+
+cd ../..
+rm -rf "$temp_dir"