ci: Add feature to use different meson versions

We want to have a branch that uses a specific branch of meson for all
tasks. Then, we can create a Cirrus cron "job" that tests Postgres
againts different meson branches.

Set a different meson branch by using `MESON_REPO` and
`MESON_BRANCH` environment variables. Use a bash script to install
this specific meson branch and rebase current Postgres branch onto
Postgres HEAD.

Fixes #81.

.cirrus.yml

@@ -27,6 +27,10 @@ env:
   TEMP_CONFIG: ${CIRRUS_WORKING_DIR}/src/tools/ci/pg_ci_base.conf
   PG_TEST_EXTRA: kerberos ldap ssl load_balance
 
+  # default variables to use in local meson installations
+  MESON_REPO: https://github.com/mesonbuild/meson.git
+  MESON_BRANCH: master
+
 
 # What files to preserve in case tests fail
 on_failure_ac: &on_failure_ac
@@ -95,6 +99,9 @@ task:
     chown root:postgres /
     chmod g+rwx /
 
+  install_meson_and_rebase_script: |
+    bash src/tools/ci/install_meson_and_rebase.sh linux
+
   configure_script: |
     su postgres <<-EOF
       meson setup \
@@ -174,6 +181,9 @@ task:
   setup_additional_packages_script: |
     #pkg install -y ...
 
+  install_meson_and_rebase_script: |
+    bash src/tools/ci/install_meson_and_rebase.sh freebsd
+
   # NB: Intentionally build without -Dllvm. The freebsd image size is already
   # large enough to make VM startup slow, and even without llvm freebsd
   # already takes longer than other platforms except for windows.
@@ -360,6 +370,9 @@ task:
         CCACHE_MAXSIZE: "400M" # tests two different builds
         SANITIZER_FLAGS: -fsanitize=alignment,undefined
 
+      install_meson_and_rebase_script: |
+        bash src/tools/ci/install_meson_and_rebase.sh linux
+
       configure_script: |
         su postgres <<-EOF
           meson setup \
@@ -485,6 +498,9 @@ task:
     brew cleanup -s # to reduce cache size
   upload_caches: homebrew
 
+  install_meson_and_rebase_script: |
+    bash src/tools/ci/install_meson_and_rebase.sh macos
+
   ccache_cache:
     folder: $CCACHE_DIR
   configure_script: |
@@ -578,6 +594,9 @@ task:
     echo 127.0.0.3 pg-loadbalancetest >> c:\Windows\System32\Drivers\etc\hosts
     type c:\Windows\System32\Drivers\etc\hosts
 
+  install_meson_and_rebase_script: |
+    bash src/tools/ci/install_meson_and_rebase.sh windows
+
   # Use /DEBUG:FASTLINK to avoid high memory usage during linking
   configure_script: |
     vcvarsall x64
@@ -643,6 +662,9 @@ task:
     %BASH% -c "where perl"
     %BASH% -c "perl --version"
 
+  install_meson_and_rebase_script: |
+    %BASH% src/tools/ci/install_meson_and_rebase.sh mingw
+
   # disable -Dnls as the number of files it creates cause a noticable slowdown
   configure_script: |
     %BASH% -c "meson setup -Ddebug=true -Doptimization=g -Dcassert=true -Db_pch=true -Dnls=disabled -DTAR=%TAR% build"

src/tools/ci/install_meson_and_rebase.sh

@@ -0,0 +1,70 @@
+#! /bin/sh
+
+set -e
+set -x
+
+CURRENT_OS=$1
+
+if [ $# -ne 1 ]; then
+    echo "install_meson_and_rebase.sh <OS>"
+    exit 1
+fi
+
+case $CURRENT_OS in
+    freebsd | linux | macos | windows | mingw)
+    ;;
+    *)
+        echo "unsupported operating system ${CURRENT_OS}"
+        exit 1
+    ;;
+esac
+
+# After repartition, hidden files are not copied. Copy them to
+# working dir
+if [ "$CURRENT_OS" = 'freebsd' ]; then
+    cp -r $CIRRUS_WORKING_DIR.orig/.[^.]* $CIRRUS_WORKING_DIR/
+    chown -R postgres:postgres .[^.]*
+fi
+
+
+# install meson by using pip
+install_meson () {
+    case $CURRENT_OS in
+        linux | windows)
+            PIP=pip
+        ;;
+        *)
+            PIP=pip3
+        ;;
+    esac
+    ${PIP} install git+${MESON_REPO}@${MESON_BRANCH}
+}
+
+run_rebase_commands() {
+    git config user.email 'postgres-ci@example.com'
+    git config user.name 'Postgres CI'
+    # windows looses the executable bit, causing an unnecessary diff
+    git config core.filemode false
+    git reset --hard
+    git remote add default-postgres https://github.com/postgres/postgres.git
+    git fetch default-postgres master
+    git rebase --no-verify default-postgres/master
+}
+
+# Rebase current branch onto Postgres HEAD
+rebase_onto_postgres () {
+    # freebsd and linux run commands as postgres user
+    case $CURRENT_OS in
+        freebsd | linux)
+su postgres <<-EOF
+    $(run_rebase_commands)
+EOF
+        ;;
+        *)
+            run_rebase_commands
+        ;;
+    esac
+}
+
+install_meson
+rebase_onto_postgres