Provide a way to apply upstream patches to the image

This change allows users to apply patches to the images during build
time directly from gerrit using the new arg PATCH.
At the moment, it's limited to upstream projects with patches on
gerrit; future changes will allow different sources, including
local directories.

Dockerfile

@@ -35,7 +35,7 @@ ENV PKGS_LIST=main-packages-list.txt
 ARG EXTRA_PKGS_LIST
 
 COPY ${PKGS_LIST} ${EXTRA_PKGS_LIST} /tmp/
-COPY prepare-image.sh /bin/
+COPY prepare-image.sh patch-image.sh /bin/
 
 RUN prepare-image.sh && \
   rm -f /bin/prepare-image.sh

README.md

@@ -43,3 +43,16 @@ The ironic configuration can be overridden by various environment variables. The
 - OS_CONDUCTOR__INSPECT_TIMEOUT=1800 - timeout (seconds) for waiting for node inspection
 - OS_CONDUCTOR__CLEAN_CALLBACK_TIMEOUT=1800 - timeout (seconds) to wait for a callback from the ramdisk doing the cleaning
 - OS_PXE__BOOT_RETRY_TIMEOUT=1200 - timeout (seconds) to enable boot retries.
+
+Applying Patches to the image
+-----------------------------
+
+When building the image, it is possible to specify a patch of one or more
+upstream projects to apply to the image, passing a file with the patch list
+using the PATCH_LIST build argument.
+At the moment, only projects hosted in opendev.org are supported.
+
+Each line of the file is in the form "project_dir refspec" where:
+- project is the last part of the project url including the org, for example openstack/ironic
+- refspec is the gerrit refspec of the patch we want to test, for example refs/changes/67/759567/1
+

patch-image.sh

@@ -0,0 +1,29 @@
+#!/usr/bin/bash
+set -ex
+
+patch_file="/tmp/${PATCH_LIST}"
+
+while IFS= read -r line
+do
+    # each line is in the form "project_dir refsspec" where:
+    # - project is the last part of the project url including the org,
+    # for example openstack/ironic
+    # - refspec is the gerrit refspec of the patch we want to test,
+    # for example refs/changes/67/759567/1
+    PROJECT=$(echo $line | cut -d " " -f1)
+    PROJ_NAME=$(echo $PROJECT | cut -d "/" -f2)
+    PROJ_URL="https://opendev.org/$PROJECT"
+    REFSPEC=$(echo $line | cut -d " " -f2)
+
+    cd /tmp
+    git clone "$PROJ_URL"
+    cd "$PROJ_NAME"
+    git fetch "$PROJ_URL" "$REFSPEC"
+    git checkout FETCH_HEAD
+
+    SKIP_GENERATE_AUTHORS=1 SKIP_WRITE_GIT_CHANGELOG=1 python3 setup.py sdist
+    pip3 install dist/*.tar.gz
+done < "$patch_file"
+
+cd /
+

prepare-image.sh

@@ -13,3 +13,9 @@ if [[ ! -z ${EXTRA_PKGS_LIST} ]]; then
 fi
 dnf clean all
 rm -rf /var/cache/{yum,dnf}/*
+if [[ ! -z ${PATCH_LIST} ]]; then
+    if [[ -s "/tmp/${PATCH_LIST}" ]]; then
+        /bin/patch-image.sh;
+    fi
+fi
+rm -f /bin/patch-image.sh