Backport all build-related commits from master to stable-0.2

This is a squash of the following commits that are required to
make gitiles buildable with the latest bazel:

9374f0a - Remove bazel-genfiles from .gitignore
bd0c596 - Use bazelisk as first choice for mvn.sh
9d5cb21 - Replace references to bazel-genfiles with bazel-bin
268d677 - Bazel: Bump bazel version to 1.0.0
03cd750 - Bazel: rules_python must be loaded now
10641da - Upgrade bazlets to latest master revision
06d3ee0 - Bazel: Introduce .bazelversion and update to 0.29.1
3de4f96 - Format all build files with buildifier
a267c30 - Bazel: Add fixes for --incompatible_load_java_rules_from_bzl
4d4432d - Upgrade bazlets to latest master revision
422d67a - Align Eclipse settings with Eclipse 2019.06
008bf1b - Update bazlets to latest revision on master

Change-Id: I4894d7beee21a0ea4bfd92c6ce3c6bf6477ef639

tools/BUILD

diff --git a/tools/BUILD b/tools/BUILD
index 6d15a21..6caa1da 100644
--- a/tools/BUILD
+++ b/tools/BUILD
@@ -3,6 +3,7 @@
     "JDK9_JVM_OPTS",
     "default_java_toolchain",
 )
+load("@rules_java//java:defs.bzl", "java_package_configuration")
 
 default_java_toolchain(
     name = "error_prone_warnings_toolchain",

tools/bazelisk_version.bzl

diff --git a/tools/bazelisk_version.bzl b/tools/bazelisk_version.bzl
new file mode 100644
index 0000000..d8b3d10
--- /dev/null
+++ b/tools/bazelisk_version.bzl
@@ -0,0 +1,16 @@
+_template = """
+load("@bazel_skylib//lib:versions.bzl", "versions")
+
+def check_bazel_version():
+  versions.check(minimum_bazel_version = "{version}")
+""".strip()
+
+def _impl(repository_ctx):
+    repository_ctx.symlink(Label("@//:.bazelversion"), ".bazelversion")
+    bazelversion = repository_ctx.read(".bazelversion").strip()
+
+    repository_ctx.file("BUILD", executable = False)
+
+    repository_ctx.file("check.bzl", executable = False, content = _template.format(version = bazelversion))
+
+bazelisk_version = repository_rule(implementation = _impl)

tools/eclipse/BUILD

diff --git a/tools/eclipse/BUILD b/tools/eclipse/BUILD
index ec640c1..68d35f4 100644
--- a/tools/eclipse/BUILD
+++ b/tools/eclipse/BUILD
@@ -1,4 +1,5 @@
 load("@com_googlesource_gerrit_bazlets//tools:classpath.bzl", "classpath_collector")
+load("@rules_java//java:defs.bzl", "java_library")
 
 DEPS = [
     "//java/com/google/gitiles:servlet",

tools/maven/mvn.sh

diff --git a/tools/maven/mvn.sh b/tools/maven/mvn.sh
index 93bef01..9b05b6f 100755
--- a/tools/maven/mvn.sh
+++ b/tools/maven/mvn.sh
@@ -49,8 +49,14 @@
   set -o xtrace
 fi
 
-bazel build //tools/maven:gen_${command} || \
-  { echo "bazel failed to build gen_${command}. Use VERBOSE=1 for more info" ; exit 1 ; }
+if [[ `which bazelisk` ]]; then
+  BAZEL_CMD=bazelisk
+else
+  BAZEL_CMD=bazel
+fi
+
+${BAZEL_CMD} build //tools/maven:gen_${command} || \
+  { echo "${BAZEL_CMD} failed to build gen_${command}. Use VERBOSE=1 for more info" ; exit 1 ; }
 
 export OUTPUT_BASE=`bazel info output_base`
-./bazel-genfiles/tools/maven/${command}.sh
+./bazel-bin/tools/maven/${command}.sh