mkosi: Replace submodules with our own thing

Unfortunately, git submodules break in all sorts of ways:

- Various github workflows (dependabot, github pages) try to do a shallow
clone of git submodules which does not work at all when the git repository
is hosted on pagure (https://pagure.io/pagure/issue/5453,
https://github.com/dependabot/dependabot-core/issues/9391).
- If the git forge hosting the git repository uses SHA256, then it breaks our
usage of it as a submodule as SHA256 repositories cannot be used as submodules
in SHA1 repositories (src.opensuse.org moved to SHA256 which broke our usage of
opensuse's systemd spec as a submodule).
- git submodules completely break usage of git worktrees.
- ...

Let's avoid all these issues by just doing our own home grown implementation of
git submodules. We lose the automatic dependabot updates this way but since dependabot
fails to run more often that not with submodules we don't really lose anything.

.github/dependabot.yml

@@ -17,8 +17,3 @@ updates:
     schedule:
       interval: "monthly"
     open-pull-requests-limit: 2
-  - package-ecosystem: "gitsubmodule"
-    directory: "/"
-    schedule:
-      interval: "daily"
-    open-pull-requests-limit: 2

.gitmodules

@@ -1,20 +0,0 @@
-[submodule "pkg/fedora"]
-	path = pkg/fedora
-	url = https://src.fedoraproject.org/rpms/systemd.git
-	branch = rawhide
-[submodule "pkg/opensuse"]
-	path = pkg/opensuse
-	url = https://code.opensuse.org/package/systemd.git
-	branch = master
-[submodule "pkg/debian"]
-	path = pkg/debian
-	url = https://salsa.debian.org/systemd-team/systemd.git
-	branch = debian/master
-[submodule "pkg/centos"]
-	path = pkg/centos
-	url = https://git.centos.org/rpms/systemd.git
-	branch = c9s-sig-hyperscale
-[submodule "pkg/arch"]
-	path = pkg/arch
-	url = https://gitlab.archlinux.org/archlinux/packaging/packages/systemd.git
-	branch = main

docs/HACKING.md

@@ -22,15 +22,6 @@ If adding a new source file, consider adding a matching test executable.
 For features at a higher level, tests in `src/test/` are very strongly recommended.
 If that is not possible, integration tests in `test/` are encouraged.
 
-```shell
-$ git config submodule.recurse true
-$ git config fetch.recurseSubmodules on-demand
-$ git config push.recurseSubmodules no
-$ cp .git/hooks/pre-commit.sample .git/hooks/pre-commit
-$ cp tools/git-submodule-update-hook.sh .git/hooks/post-rewrite
-$ cp tools/git-submodule-update-hook.sh .git/hooks/post-checkout
-```
-
 Please always test your work before submitting a PR.
 For many of the components of systemd testing is straightforward as you can simply compile systemd and run the relevant tool from the build directory.
 

mkosi.images/system/mkosi.conf.d/10-arch/mkosi.conf

@@ -4,6 +4,11 @@
 Distribution=arch
 
 [Content]
+Environment=
+        GIT_URL=https://gitlab.archlinux.org/archlinux/packaging/packages/systemd.git
+        GIT_BRANCH=main
+        GIT_COMMIT=dc6c099e0785753c1c88b4adcbcbfc209a8d12e3
+
 VolatilePackages=
         systemd
         systemd-libs

mkosi.images/system/mkosi.conf.d/10-centos/mkosi.conf

@@ -4,6 +4,11 @@
 Distribution=centos
 
 [Content]
+Environment=
+        GIT_URL=https://git.centos.org/rpms/systemd.git
+        GIT_BRANCH=c9s-sig-hyperscale
+        GIT_COMMIT=8cf2aed0181920611421384f7374720db269d6c7
+
 Packages=
         kernel-modules # For squashfs
         rpmautospec-rpm-macros

mkosi.images/system/mkosi.conf.d/10-debian-ubuntu/mkosi.conf

@@ -5,6 +5,11 @@ Distribution=|debian
 Distribution=|ubuntu
 
 [Content]
+Environment=
+        GIT_URL=https://salsa.debian.org/systemd-team/systemd.git
+        GIT_BRANCH=debian/master
+        GIT_COMMIT=18201fa98d74172fa1a17242326e3275995cde13
+
 VolatilePackages=
         libnss-myhostname
         libnss-mymachines

mkosi.images/system/mkosi.conf.d/10-fedora/mkosi.conf

@@ -4,6 +4,11 @@
 Distribution=fedora
 
 [Content]
+Environment=
+        GIT_URL=https://src.fedoraproject.org/rpms/systemd.git
+        GIT_BRANCH=rawhide
+        GIT_COMMIT=74810c5bc4fe7d872e54c253447ffd61bbc8839f
+
 Packages=
         btrfs-progs
         compsize

mkosi.images/system/mkosi.conf.d/10-opensuse/mkosi.conf

@@ -7,6 +7,11 @@ Distribution=opensuse
 InitrdInclude=initrd/
 
 [Content]
+Environment=
+        GIT_URL=https://src.opensuse.org/rpm/systemd
+        GIT_BRANCH=factory
+        GIT_COMMIT=28c9bef337dd47c88adc1d948cedfdc79c788e2955f17a534bd76da6419722dd
+
 VolatilePackages=
         systemd
         systemd-boot

mkosi.images/system/mkosi.sync

@@ -2,8 +2,21 @@
 # SPDX-License-Identifier: LGPL-2.1-or-later
 set -e
 
-if [ -z "$(ls --almost-all "pkg/$DISTRIBUTION")" ] || [ -f "pkg/$DISTRIBUTION/.git" ]; then
-    PKG_SUBDIR="$(realpath "pkg/$DISTRIBUTION" --relative-to "$PWD")"
-    git submodule sync "$PKG_SUBDIR"
-    git submodule update --init "$PKG_SUBDIR"
+if ((NO_SYNC)); then
+    exit 0
 fi
+
+PKG_SUBDIR="$(realpath --canonicalize-missing "pkg/$DISTRIBUTION" --relative-to "$PWD")"
+
+if [[ -d "$PKG_SUBDIR/.git" ]] && [[ "$(git -C "$PKG_SUBDIR" rev-parse HEAD)" == "$GIT_COMMIT" ]]; then
+    exit 0
+fi
+
+if [[ ! -e "$PKG_SUBDIR" ]] || [[ -z "$(ls --almost-all "$PKG_SUBDIR")" ]]; then
+    git clone "$GIT_URL" --branch "$GIT_BRANCH" "$PKG_SUBDIR"
+else
+    git -C "$PKG_SUBDIR" remote set-url origin "$GIT_URL"
+    git -C "$PKG_SUBDIR" fetch origin "$GIT_BRANCH"
+fi
+
+git -C "$PKG_SUBDIR" -c advice.detachedHead=false checkout "$GIT_COMMIT"

tools/git-setup.sh

@@ -4,12 +4,6 @@ set -eu
 
 cd "${MESON_SOURCE_ROOT:?}"
 
-if [ -e .git ]; then
-    git config submodule.recurse true
-    git config fetch.recurseSubmodules on-demand
-    git config push.recurseSubmodules no
-fi
-
 ret=2
 
 if [ -f .git/hooks/pre-commit.sample ] && [ ! -f .git/hooks/pre-commit ]; then
@@ -19,16 +13,4 @@ if [ -f .git/hooks/pre-commit.sample ] && [ ! -f .git/hooks/pre-commit ]; then
     ret=0
 fi
 
-if [ ! -f .git/hooks/post-rewrite ]; then
-    cp -p tools/git-submodule-update-hook.sh .git/hooks/post-rewrite
-    echo 'Activated post-rewrite hook'
-    ret=0
-fi
-
-if [ ! -f .git/hooks/post-checkout ]; then
-    cp -p tools/git-submodule-update-hook.sh .git/hooks/post-checkout
-    echo 'Activated post-checkout hook'
-    ret=0
-fi
-
 exit $ret

tools/git-submodule-update-hook.sh

@@ -1,4 +0,0 @@
-#!/bin/sh
-# SPDX-License-Identifier: LGPL-2.1-or-later
-
-exec git submodule update