vmtest: #121 follow-ups. Loop increase bpf-next git fetch depth

- The previously introduced git fetch depth of bpf-next tree is not sufficient
when bpf-next tree is far ahead from libbpf checkpoint commit, so increase the
depth up to 128 max. Since 128 may be an overkill for a general case, increase
exponentially in a loop until max is reached.

- Do not fetch bpf-next twice
- Remove setup_example.sh

.travis.yml

@@ -11,7 +11,6 @@ env:
         - CI_MANAGERS="$TRAVIS_BUILD_DIR/travis-ci/managers"
         - VMTEST_ROOT="$TRAVIS_BUILD_DIR/travis-ci/vmtest"
         - REPO_ROOT="$TRAVIS_BUILD_DIR"
-        - GIT_FETCH_DEPTH=64
         - VMTEST_SETUPCMD="PROJECT_NAME=${PROJECT_NAME} ./${PROJECT_NAME}/travis-ci/vmtest/run_selftests.sh"
     jobs:
         # Setup command override.
@@ -37,8 +36,7 @@ before_script:
     - sudo apt-get -qq update
     - sudo apt-get -y install dwarves=1.15-1
     - sudo apt-get -qq -y install clang-10 lld-10 llvm-10
-    - if [[ "${KERNEL}" = 'LATEST' ]]; then ${VMTEST_ROOT}/build_latest_kernel.sh travis-ci/vmtest/bpf-next; fi
-    - ${VMTEST_ROOT}/prepare_selftests.sh travis-ci/vmtest/bpf-next
+    - KERNEL="${KERNEL}" ${VMTEST_ROOT}/prepare_selftests.sh travis-ci/vmtest/bpf-next
     # Escape whitespace characters.
     - setup_cmd=$(sed 's/\([[:space:]]\)/\\\1/g' <<< "${VMTEST_SETUPCMD}")
     - if [[ "${KERNEL}" = 'LATEST' ]]; then

travis-ci/vmtest/build_latest_kernel.sh

@@ -1,8 +0,0 @@
-#!/bin/bash
-
-set -eux
-
-GIT_FETCH_DEPTH="${GIT_FETCH_DEPTH}" ${VMTEST_ROOT}/checkout_latest_kernel.sh $1
-cd $1
-cp ${VMTEST_ROOT}/configs/latest.config .config
-make -j $((4*$(nproc))) olddefconfig all

travis-ci/vmtest/checkout_latest_kernel.sh

@@ -17,8 +17,8 @@ if [ ! -d "${REPO_PATH}" ]; then
 	cd ${REPO_PATH}
 	git init
 	git remote add bpf-next ${BPF_NEXT_ORIGIN}
-	git fetch --depth ${GIT_FETCH_DEPTH} bpf-next
-	git reset --hard ${LINUX_SHA}
-else
-	cd ${REPO_PATH}
+	for depth in 32 64 128; do
+		git fetch --depth ${depth} bpf-next
+		git reset --hard ${LINUX_SHA} && break
+	done
 fi

travis-ci/vmtest/prepare_selftests.sh

@@ -1,11 +1,19 @@
 #!/bin/bash
 
 set -eux
-GIT_FETCH_DEPTH="${GIT_FETCH_DEPTH}" ${VMTEST_ROOT}/checkout_latest_kernel.sh $1
+
+REPO_PATH=$1
+
+${VMTEST_ROOT}/checkout_latest_kernel.sh ${REPO_PATH}
+cd ${REPO_PATH}
+
+if [[ "${KERNEL}" = 'LATEST' ]]; then
+	cp ${VMTEST_ROOT}/configs/latest.config .config
+	make -j $((4*$(nproc))) olddefconfig all
+fi
 
 # Fix runqslower build
 # TODO(hex@): remove after the patch is merged from bpf to bpf-next tree
-cd $1
 wget https://lore.kernel.org/bpf/908498f794661c44dca54da9e09dc0c382df6fcb.1580425879.git.hex@fb.com/t.mbox.gz
 gunzip t.mbox.gz
 git apply t.mbox

travis-ci/vmtest/setup_example.sh

@@ -1,11 +0,0 @@
-#!/bin/sh
-
-# An example of a script run on VM boot.
-# To execute it in TravisCI set VMTEST_SETUPCMD env var of .travis.yml in
-# libbpf root folder, e.g.
-# VMTEST_SETUPCMD="./${PROJECT_NAME}/travis-ci/vmtest/setup_example.sh"
-
-if [ ! -z "${PROJECT_NAME}" ]; then
-	echo "Running ${PROJECT_NAME} setup scripts..."
-fi
-echo "Hello, ${USER}!"