Merge lp:~adam-collard/ols-jenkaas/detect-git-changes-again into lp:~ols-jenkaas-admins/ols-jenkaas/trunk

[Adam Collard]

Don't blindly copy the tip to the old_tip - munge it in place

Previous attempts at munging the old_tip were buggy:
 - bash and awk quoting/escaping bugs
 - truncation of input file which was also output file later in the pipeline

This version was tested in a subshell with REFS and OLD_TIP defined.

Verified that the environment has the necessary version (>= 4.1.0) of gawk installed (actually 4.1.3)

[lp:~adam-collard/ols-jenkaas/detect-git-changes-again]

591. By Adam Collard on 2018-04-19

Replace gawk wonder with simpler printf

[Guillermo Gonzalez (verterok)]

LGTM, let's try it!

review: Approve

[Colin Watson (cjwatson)]

review: Approve

=== modified file 'project/detect-changes'
--- project/detect-changes	2018-04-14 03:17:53 +0000
+++ project/detect-changes	2018-04-19 11:23:24 +0000
@@ -25,8 +25,9 @@
 OLD_TIP_URL=${JENKINS_URL}/job/${JOB_NAME}/lastSuccessfulBuild/artifact/tip
 OLD_TIP=${WORKSPACE}/old_tip
 
-# wget will create an empty file if the artifact doesn't exist
-wget -q ${OLD_TIP_URL} -O ${OLD_TIP} || echo > ${OLD_TIP}
+touch ${OLD_TIP}
+# Assume out of date if we've lost the history of the last successful build
+wget -q ${OLD_TIP_URL} -O ${OLD_TIP} || true
 
 # Introspect
 . ~/.config/jenkaas/environment
@@ -50,8 +51,11 @@
     bzr version-info --custom --template ${INFO} "{revision_id}" ${TRUNK} > ${TIP}
 else
     git ls-remote ${TRUNK} $REFS > ${TIP}
-    # if refs don't match, ignore it
-    grep ${REFS} ${OLD_TIP} || cp ${TIP} ${OLD_TIP} || true 
+    # if refs don't match,  we munge the old tip to look like current tip.
+    if ! grep "$REFS" "$OLD_TIP" > /dev/null ; then
+        printf '%s\t%s\n' "$(cut -f1 "$OLD_TIP")" "$REFS" > "$OLD_TIP.new"
+        mv "$OLD_TIP.new" "$OLD_TIP"
+    fi
 fi
 
 # Succeed if a new tip appears