Add diskimage-create arg for Octavia Git branch

Use `-g` to select the current Git branch to use for the amphora
build. This has historically been confusing for people, and this should
make it a little easier.

Change-Id: Iab01faaa17507c7bea399db7ee8f27f88d8de183

diskimage-create/README.rst

@@ -104,6 +104,7 @@ Command syntax:
             [-d **bionic**/**8** | <other release id> ]
             [-e]
             [-f]
+            [-g **repository branch** | stable/train | stable/stein | ... ]
             [-h]
             [-i **ubuntu-minimal** | fedora | centos-minimal | rhel ]
             [-k <kernel package name> ]
@@ -124,6 +125,7 @@ Command syntax:
         '-d' distribution release id (default on ubuntu: bionic)
         '-e' enable complete mandatory access control systems when available (default: permissive)
         '-f' disable tmpfs for build
+        '-g' build the image for a specific OpenStack Git branch (default: current repository branch)
         '-h' display help message
         '-i' is the base OS (default: ubuntu-minimal)
         '-k' is the kernel meta package name, currently only for ubuntu-minimal base OS (default: linux-image-virtual)
@@ -139,6 +141,66 @@ Command syntax:
         '-x' enable tracing for diskimage-builder
 
 
+Building Images for Alternate Branches
+======================================
+
+By default, the diskimage-create.sh script will build an amphora image using
+the Octavia Git branch of the repository. If you need an image for a specific
+branch, such as "stable/train", you need to specify the "-g" option with the
+branch name. An example for "stable/train" would be:
+
+.. code-block:: bash
+
+   diskimage-create.sh -g stable/train
+
+Advanced Git Branch/Reference Based Images
+------------------------------------------
+
+If you need to build an image from a local repository or with a specific Git
+reference or branch, you will need to set some environment variables for
+diskimage-builder.
+
+.. note::
+
+    These advanced settings will override the "-g" diskimage-create.sh setting.
+
+Building From a Local Octavia Repository
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Set the DIB_REPOLOCATION_amphora_agent variable to the location of the Git
+repository containing the amphora agent:
+
+.. code-block:: bash
+
+   export DIB_REPOLOCATION_amphora_agent=/opt/stack/octavia
+
+Building With a Specific Git Reference
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Set the DIB_REPOREF_amphora_agent variable to point to the Git branch or
+reference of the amphora agent:
+
+.. code-block:: bash
+
+   export DIB_REPOREF_amphora_agent=refs/changes/40/674140/7
+
+See the `Environment Variables`_ section below for additional information and
+examples.
+
+Amphora Agent Upper Constraints
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+You may also need to specify which version of the OpenStack
+upper-constraints.txt file will be used to build the image. For example, to
+specify the "stable/train" upper constraints Git branch, set the following
+environment variable:
+
+.. code-block:: bash
+
+   export DIB_REPOLOCATION_upper_constraints=https://opendev.org/openstack/requirements/raw/branch/stable/train/upper-constraints.txt
+
+See `Dependency Management for OpenStack Projects <https://docs.openstack.org/project-team-guide/dependency-management.html>`_ for more information.
+
 Environment Variables
 =====================
 These are optional environment variables that can be set to override the script
@@ -150,12 +212,18 @@ DIB_REPOLOCATION_amphora_agent
     - Example: /tmp/octavia
 
 DIB_REPOREF_amphora_agent
-    - The git reference to checkout for the amphora-agent code inside the
+    - The Git reference to checkout for the amphora-agent code inside the
       image.
-    - Default: master
+    - Default: The current branch
     - Example: stable/stein
     - Example: refs/changes/40/674140/7
 
+DIB_REPOLOCATION_upper_constraints
+    - Location of the upper-constraints.txt file used for the image.
+    - Default: The upper-constraints.txt for the current branch
+    - Example: https://opendev.org/openstack/requirements/raw/branch/master/upper-constraints.txt
+    - Example: https://opendev.org/openstack/requirements/raw/branch/stable/train/upper-constraints.txt
+
 CLOUD_INIT_DATASOURCES
     - Comma separated list of cloud-int datasources
     - Default: ConfigDrive

diskimage-create/diskimage-create.sh

@@ -26,6 +26,7 @@ usage() {
     echo "            [-d **bionic**/**8** | <other release id> ]"
     echo "            [-e]"
     echo "            [-f]"
+    echo "            [-g **repository branch** | stable/train | stable/stein | ... ]"
     echo "            [-h]"
     echo "            [-i **ubuntu-minimal** | fedora | centos-minimal | rhel ]"
     echo "            [-k <kernel package name> ]"
@@ -46,6 +47,7 @@ usage() {
     echo "        '-d' distribution release id (default on ubuntu: bionic)"
     echo "        '-e' enable complete mandatory access control systems when available (default: permissive)"
     echo "        '-f' disable tmpfs for build"
+    echo "        '-g' build the image for a specific OpenStack Git branch (default: current repository branch)"
     echo "        '-h' display this help message"
     echo "        '-i' is the base OS (default: ubuntu-minimal)"
     echo "        '-k' is the kernel meta package name, currently only for ubuntu-minimal base OS (default: linux-image-virtual)"
@@ -89,7 +91,7 @@ dib_enable_tracing=
 
 AMP_LOGFILE=""
 
-while getopts "a:b:c:d:efhi:k:l:no:pt:r:s:vw:x" opt; do
+while getopts "a:b:c:d:efg:hi:k:l:no:pt:r:s:vw:x" opt; do
     case $opt in
         a)
             AMP_ARCH=$OPTARG
@@ -121,6 +123,20 @@ while getopts "a:b:c:d:efhi:k:l:no:pt:r:s:vw:x" opt; do
         f)
             AMP_DISABLE_TMP_FS='--no-tmpfs'
         ;;
+        g)
+            if [ -z "$DIB_REPOREF_amphora_agent" ]; then
+                echo "Building image with amphora agent from $OPTARG."
+                export DIB_REPOREF_amphora_agent=$OPTARG
+            else
+                echo "Environment variable DIB_REPOREF_amphora_agent is set. Building the image with amphora agent $DIB_REPOREF_amphora_agent."
+            fi
+            if [ -z "$DIB_REPOLOCATION_upper_constraints" ]; then
+                echo "Using upper constraints from https://opendev.org/openstack/requirements/raw/branch/$OPTARG/upper-constraints.txt."
+                export DIB_REPOLOCATION_upper_constraints="https://opendev.org/openstack/requirements/raw/branch/$OPTARG/upper-constraints.txt"
+            else
+                echo "Environment variable DIB_REPOLOCATION_upper_constraints is set. Building the image with upper-constraints.txt from $DIB_REPOLOCATION_upper_constraints."
+            fi
+        ;;
         h)
             usage
         ;;

releasenotes/notes/diskimage-create-git-branch-9c44e7e3fa70a985.yaml

@@ -0,0 +1,5 @@
+---
+features:
+  - |
+    Added an option to the diskimage-create.sh script to specify the Octavia
+    Git branch to build the image from.