Enable pre-commit tool linting

This should help use keep the codebase more consistent, and avoid sevel
whitespace related issues, or bad file permissions.

pre-commit allows us to easily introduce other linters in follow-ups,
like bashate.

Note: pre-commit tool does *not* install any git-hooks. Making commits
will will call the tool unless you deliverately tell it to install the
hooks.

Signed-off-by: Sorin Sbarnea <ssbarnea@redhat.com>

.pre-commit-config.yaml

@@ -0,0 +1,12 @@
+---
+exclude: ^vendor/
+repos:
+  - repo: https://github.com/pre-commit/pre-commit-hooks.git
+    rev: v2.4.0
+    hooks:
+      - id: end-of-file-fixer
+      - id: trailing-whitespace
+      - id: mixed-line-ending
+      - id: check-byte-order-marker
+      - id: check-executables-have-shebangs
+      - id: check-merge-conflict

Makefile

@@ -32,8 +32,10 @@ BUILDTAGS ?= \
 	exclude_graphdriver_devicemapper \
 	seccomp \
 	varlink
-PYTHON ?= $(shell command -v python python3|head -n1)
+PYTHON ?= $(shell command -v python3 python|head -n1)
 PKG_MANAGER ?= $(shell command -v dnf yum|head -n1)
+# ~/.local/bin is not in PATH on all systems
+PRE_COMMIT = $(shell command -v bin/venv/bin/pre-commit ~/.local/bin/pre-commit pre-commit | head -n1)
 
 SOURCES = $(shell find . -name "*.go")
 
@@ -149,6 +151,11 @@ endif
 	touch $@
 
 lint: golangci-lint
+ifeq ($(PRE_COMMIT),)
+	@echo "FATAL: pre-commit was not found, check https://pre-commit.com/ about installing it." >&2
+	@exit 2
+endif
+	$(PRE_COMMIT) run -a
 
 golangci-lint: .gopathok varlink_generate .install.golangci-lint
 	$(GOBIN)/golangci-lint run --tests=false --skip-files swagger.go

contrib/gate/Dockerfile

@@ -48,6 +48,7 @@ WORKDIR $GOSRC
 RUN set -x && \
     make install.tools && \
     install -D -m 755 $GOSRC/contrib/gate/entrypoint.sh /usr/local/bin/ && \
+    python3 -m pip install pre-commit && \
     rm -rf "$GOSRC"
 
 # Install cni config