round-robin-bisect.sh: Make code to trigger follow-up builds more robust

... and with better comments.

Change-Id: I9e61b94e382d265daeae6cc8fd4ba5ab9f83bb68

1 files changed, 36 insertions, 15 deletions

diff --git a/round-robin-bisect.sh b/round-robin-bisect.sh
index 016d0883..fb702166 100755
--- a/round-robin-bisect.sh
+++ b/round-robin-bisect.sh
@@ -456,8 +456,44 @@ else
     first_bad=$(git rev-parse HEAD)
     push_interesting_commit $first_bad "bad-merge-base"
 fi
+
+# Bisect if officially over.
 cd ..
 
+# Create trigger-build-* files for subsequent builds.
+if ! [ -f $artifacts/build-$bad_rev/trigger-build-$current_project ]; then
+    # This can happen *only* when replaying bisects.
+    # Otherwise $bad_rev is always tested second to $baseline_rev.
+    bad_build=$(find $artifacts -path "$artifacts/build-*/trigger-build-$current_project" | tail -n1)
+    assert_with_msg "No bad build during this bisect" [ x"$bad_build" != x"" ]
+    mkdir -p $artifacts/build-$bad_rev
+    cp $bad_build $artifacts/build-$bad_rev/trigger-build-$current_project
+    sed -i -e "s/^${current_project}_branch=.*\$/${current_project}_branch=$bad_rev/" \
+	$artifacts/build-$bad_rev/trigger-build-$current_project
+fi
+
+if ! [ -f $artifacts/build-$first_bad/trigger-build-$current_project ]; then
+    # This is rare, but git bisect can infer that a commit is first-bad
+    # without actually testing it.  Workaround by constructing trigger-build
+    # file from that of $bad_rev's.
+    mkdir -p $artifacts/build-$first_bad
+    cp $artifacts/build-$bad_rev/trigger-build-$current_project \
+       $artifacts/build-$first_bad/trigger-build-$current_project
+    sed -i -e "s/$first_bad/$bad_rev/" $artifacts/trigger-build-2-default
+fi
+
+if ! [ -f $artifacts/trigger-build-1-advance ]; then
+    # Reset baseline to the regressed commit so that we will catch subsequent
+    # regressions (worse than $bad_rev).
+    cp $artifacts/build-$first_bad/trigger-build-$current_project \
+       $artifacts/trigger-build-1-reset
+    echo "update_baseline=reset" >> $artifacts/trigger-build-1-reset
+fi
+
+# Trigger master build now instead of waiting for next timed SCM trigger.
+cp $artifacts/build-$bad_rev/trigger-build-$current_project \
+   $artifacts/trigger-build-2-default
+
 # Save BISECT_* logs
 find "$current_project" -path "$current_project/.git/BISECT_*" -print0 | xargs -0 -I@ mv @ $artifacts/git-logs/
 
@@ -644,19 +680,4 @@ $CI_MAIL_RECIPIENTS
 EOF
 fi
 
-# Reset baseline to the regressed commit so that we will catch subsequent
-# regressions (worse than $bad_rev).
-cp $artifacts/build-$first_bad/trigger-build-$current_project $artifacts/trigger-build-1-reset
-echo "update_baseline=reset" >> $artifacts/trigger-build-1-reset
-
-# Trigger master build now instead of waiting for next timed SCM trigger.
-if [ -f $artifacts/build-$bad_rev/trigger-build-$current_project ]; then
-    cp $artifacts/build-$bad_rev/trigger-build-$current_project $artifacts/trigger-build-2-default
-else
-    # When replaying a bisect we often skip the $bad_rev build, so we won't
-    # have its artifacts.  Use $first_bad's trigger-build-* instead.
-    cp $artifacts/build-$first_bad/trigger-build-$current_project $artifacts/trigger-build-2-default
-    sed -i -e "s/$first_bad/$bad_rev/" $artifacts/trigger-build-2-default
-fi
-
 trap "" EXIT