From 4c7a3bf79fca93351477c344e4129f663a2d5ce1 Mon Sep 17 00:00:00 2001
From: Chris Jones <cmsj@tenshu.net>
Date: Fri, 20 Dec 2013 14:35:34 +0000
Subject: [PATCH] Improve source-repositories git caching.

We now unconditionally cache the repositories being fetched with
source-repositories.

Additionally, by improving the way we handle repository refs, we are now
able to build images with code taken directly from gerrit reviews.

Change-Id: Ifd4c5691f6761eb5551663e6d0aa1c0e42afced3
---
 elements/source-repositories/README.md        |  7 ++++
 .../extra-data.d/98-source-repositories       | 42 +++++++++----------
 2 files changed, 27 insertions(+), 22 deletions(-)

diff --git a/elements/source-repositories/README.md b/elements/source-repositories/README.md
index 548d1b8b0..5d0003d9f 100644
--- a/elements/source-repositories/README.md
+++ b/elements/source-repositories/README.md
@@ -29,6 +29,13 @@ mirror you could set DIB_REPOLOCATION_ironic=git://localgitserver/ironic.git
 Alternatively if you would like to use the keystone element and build an image with
 keystone from a stable branch then you would set DIB_REPOREF_keystone=stable/grizzly
 
+If you wish to build an image using code from a gerrit review, you can set 
+DIB_REPOLOCATION_<name> and DIB_REPOREF_<name> to the values given by gerrit in the
+fetch/pull section of a review. For example:
+
+    DIB_REPOLOCATION_nova=https://review.openstack.org/openstack/nova
+    DIB_REPOREF_nova=refs/changes/72/61972/8
+
 Git sources will be cloned to \<destination\>
 
 Tarballs will be extracted to \<destination\>. Tarballs should contain a
diff --git a/elements/source-repositories/extra-data.d/98-source-repositories b/elements/source-repositories/extra-data.d/98-source-repositories
index 2b603bd0f..0b9d41a5e 100755
--- a/elements/source-repositories/extra-data.d/98-source-repositories
+++ b/elements/source-repositories/extra-data.d/98-source-repositories
@@ -35,38 +35,36 @@ function get_repos_for_element(){
             # REPOLOCATION can be overridden with DIB_REPOLOCATION_{name}
             local REPOLOCATION_OVERRIDE=DIB_REPOLOCATION_${REPONAME//-/_}
             REPOLOCATION=${!REPOLOCATION_OVERRIDE:-$REPOLOCATION}
-            if [ "$REPOLOCATION" = "$REPO_ORIG_LOCATION" ] ; then
-                # We're pulling from the element specified repo, do caching for
-                # the user.
-                CACHE_NAME=$(echo $REPOLOCATION | sha1sum | awk '{ print $1 }' )
-                CACHE_PATH=~/.cache/image-create/repository-sources/$CACHE_NAME
-            else
-                CACHE_PATH=''
-            fi
 
             # REPOREF can be overridden with DIB_REPOREF_{name}
             local REPOREF_OVERRIDE=DIB_REPOREF_${REPONAME//-/_}
             REPOREF=${!REPOREF_OVERRIDE:-$REPOREF}
 
+            # Determine a unique cache path for this repo
+            CACHE_NAME=$(echo "${REPOTYPE}_${REPOLOCATION}" | sha1sum | awk '{ print $1 }' )
+            CACHE_PATH=~/.cache/image-create/repository-sources/$CACHE_NAME
+
             case $REPOTYPE in
             git)
-                echo "Fetching $REPONAME git repository from $REPOLOCATION($REPOREF)"
                 sudo mkdir -p $REPO_SUB_DIRECTORY
-                if [ -n "$CACHE_PATH" ] ; then
-                    echo "Caching $REPONAME source repository in $CACHE_PATH"
-                    if [ ! -e "$CACHE_PATH" ] ; then
-                        git clone $REPOLOCATION $CACHE_PATH.tmp
-                        mv ${CACHE_PATH}{.tmp,}
-                    elif [ -z "$DIB_OFFLINE" ] ; then
-                        git --git-dir=$CACHE_PATH/.git fetch
-                        git --git-dir=$CACHE_PATH/.git --work-tree=$CACHE_PATH reset --hard origin/master
-                    fi
-                    sudo git clone $CACHE_PATH $REPO_DEST
-                else
-                    sudo git clone $REPOLOCATION $REPO_DEST
+
+                if [ ! -e "$CACHE_PATH" ] ; then
+                    echo "Caching $REPONAME from $REPOLOCATION in $CACHE_PATH"
+                    git clone $REPOLOCATION $CACHE_PATH.tmp
+                    mv ${CACHE_PATH}{.tmp,}
                 fi
+
+                HAS_REF=$(git --git-dir=$CACHE_PATH/.git show-ref $REPOREF || true)
+                if [ -z "$DIB_OFFLINE" -o -z "$HAS_REF" ] ; then
+                    echo "Updating cache of $REPOLOCATION in $CACHE_PATH with ref $REPOREF"
+                    git --git-dir=$CACHE_PATH/.git fetch --update-head-ok $REPOLOCATION ${REPOREF}:${REPOREF}
+                fi
+
+                echo "Cloning from $REPONAME cache and applying ref $REPOREF"
+                sudo git clone $CACHE_PATH $REPO_DEST
                 pushd $REPO_DEST
-                sudo git reset --hard $REPOREF
+                sudo git fetch $CACHE_PATH $REPOREF
+                sudo git reset --hard FETCH_HEAD
                 popd
                 ;;
             tar)