Add support for Podman as well as Docker (#1026)

Would like to see this package work on systems without Docker installed
which have Podman.

Signed-off-by: Daniel J Walsh <dwalsh@redhat.com>

Makefile

@@ -2,6 +2,7 @@ MAKEFLAGS += --warn-undefined-variables
 SHELL := /bin/bash
 .SHELLFLAGS := -o pipefail -euc
 .DEFAULT_GOAL := install
+ENGINE := $(shell { command -v podman || command -v docker; } 2>/dev/null)
 
 include Makefile.variables
 
@@ -33,7 +34,7 @@ clean:
 
 ## prefix before other make targets to run in your local dev environment
 local: | quiet
-	@$(eval DOCKRUN= )
+	@$(eval ENGINERUN= )
 	@mkdir -p tmp
 	@touch tmp/dev_image_id
 quiet: # this is silly but shuts up 'Nothing to be done for `local`'
@@ -42,9 +43,9 @@ quiet: # this is silly but shuts up 'Nothing to be done for `local`'
 prepare: tmp/dev_image_id
 tmp/dev_image_id: Dockerfile.dev scripts/devtools.sh
 	@mkdir -p tmp
-	@docker rmi -f ${DEV_IMAGE} > /dev/null 2>&1 || true
-	@docker build -t ${DEV_IMAGE} -f Dockerfile.dev .
-	@docker inspect -f "{{ .ID }}" ${DEV_IMAGE} > tmp/dev_image_id
+	@${ENGINE} rmi -f ${DEV_IMAGE} > /dev/null 2>&1 || true
+	@${ENGINE} build -t ${DEV_IMAGE} -f Dockerfile.dev .
+	@${ENGINE} inspect -f "{{ .ID }}" ${DEV_IMAGE} > tmp/dev_image_id
 
 # ----------------------------------------------
 # build
@@ -54,60 +55,61 @@ build: build/dev
 .PHONY: build/dev
 build/dev: test *.go
 	@mkdir -p bin/
-	${DOCKRUN} go build --ldflags "$(LDFLAGS)"
-	${DOCKRUN} bash ./scripts/acceptance.sh
+	${ENGINERUN} go build --ldflags "$(LDFLAGS)"
+	${ENGINERUN} bash ./scripts/acceptance.sh
 
 ## Compile the project for multiple OS and Architectures.
 xcompile: check
 	@rm -rf build/
 	@mkdir -p build
-	${DOCKRUN} bash ./scripts/xcompile.sh
+	${ENGINERUN} bash ./scripts/xcompile.sh
 	@find build -type d -exec chmod 755 {} \; || :
 	@find build -type f -exec chmod 755 {} \; || :
 
 .PHONY: install
 install: build
-	${DOCKRUN} go install
+	${ENGINERUN} go install
 
 # Each of the fetch should be an entry within vendor.json; not currently included within project
 .PHONY: vendor
 vendor: tmp/dev_image_id
-	${DOCKRUN} go mod vendor
+	@mkdir -p vendor
+	${ENGINERUN} go mod vendor
 
 # ----------------------------------------------
 # develop and test
 
 .PHONY: format
 format: vendor
-	${DOCKRUN} bash ./scripts/format.sh
+	${ENGINERUN} bash ./scripts/format.sh
 
 
 .PHONY: secure
 secure: format
-	${DOCKRUN} bash ./scripts/secure.sh
+	${ENGINERUN} bash ./scripts/secure.sh
 
 .PHONY: check
 check: secure
-	${DOCKRUN} bash ./scripts/check.sh
+	${ENGINERUN} bash ./scripts/check.sh
 
 
 
 .PHONY: test
 test: check
-	${DOCKRUN} bash ./scripts/test.sh
+	${ENGINERUN} bash ./scripts/test.sh
 
 .PHONY: cover
 cover: check
 	@rm -rf cover/
 	@mkdir -p cover
-	${DOCKRUN} bash ./scripts/coverage.sh
+	${ENGINERUN} bash ./scripts/coverage.sh
 	@find cover -type d -exec chmod 755 {} \; || :
 	@find cover -type f -exec chmod 644 {} \; || :
 
 
 .PHONY: release
 release: xcompile
-	${DOCKRUN} bash ./scripts/publish.sh
+	${ENGINERUN} bash ./scripts/publish.sh
 
 # ----------------------------------------------
 # utilities

Makefile.variables

@@ -29,7 +29,7 @@ endif
 
 DEV_IMAGE := ${PROJECT}_dev
 
-DOCKRUN := docker run --rm \
+ENGINERUN := ${ENGINE} run --rm \
 	-e LDFLAGS="${LDFLAGS}" \
 	-e GITHUB_TOKEN="${GITHUB_TOKEN}" \
 	-v ${ROOT}/vendor:/go/src \

README.md

@@ -5,7 +5,7 @@
 
 a lightweight and portable command-line YAML processor. `yq` uses [jq](https://github.com/stedolan/jq) like syntax but works with yaml files as well as json. It doesn't yet support everything `jq` does - but it does support the most common operations and functions, and more is being added continuously.
 
-yq is written in go - so you can download a dependency free binary for your platform and you are good to go! If you prefer there are a variety of package managers that can be used as well as docker, all listed below.
+yq is written in go - so you can download a dependency free binary for your platform and you are good to go! If you prefer there are a variety of package managers that can be used as well as Docker and Podman, all listed below.
 
 ## Quick Usage Guide
 
@@ -96,7 +96,7 @@ sudo mv /etc/myfile.tmp /etc/myfile
 rm /etc/myfile.tmp
 ```
 
-### Run with Docker
+### Run with Docker or Podman
 
 #### Oneshot use:
 
@@ -104,6 +104,10 @@ rm /etc/myfile.tmp
 docker run --rm -v "${PWD}":/workdir mikefarah/yq <command> [flags] [expression ]FILE...
 ```
 
+```bash
+podman run --rm -v "${PWD}":/workdir mikefarah/yq <command> [flags] [expression ]FILE...
+```
+
 #### Pipe in via STDIN:
 
 You'll need to pass the `-i\--interactive` flag to docker:
@@ -112,12 +116,20 @@ You'll need to pass the `-i\--interactive` flag to docker:
 cat myfile.yml | docker run -i --rm mikefarah/yq e . -
 ```
 
+```bash
+cat myfile.yml | podman run -i --rm mikefarah/yq e . -
+```
+
 #### Run commands interactively:
 
 ```bash
 docker run --rm -it -v "${PWD}":/workdir --entrypoint sh mikefarah/yq
 ```
 
+```bash
+podman run --rm -it -v "${PWD}":/workdir --entrypoint sh mikefarah/yq
+```
+
 It can be useful to have a bash function to avoid typing the whole docker command:
 
 ```bash
@@ -126,17 +138,27 @@ yq() {
 }
 ```
 
+```bash
+yq() {
+  podman run --rm -i -v "${PWD}":/workdir mikefarah/yq "$@"
+}
+```
+
 
 #### Running as root:
 
-`yq`'s docker image no longer runs under root (https://github.com/mikefarah/yq/pull/860). If you'd like to install more things in the docker image, or you're having permissions issues when attempting to read/write files you'll need to either:
+`yq`'s container image no longer runs under root (https://github.com/mikefarah/yq/pull/860). If you'd like to install more things in the container image, or you're having permissions issues when attempting to read/write files you'll need to either:
 
 
 ```
 docker run --user="root" -it --entrypoint sh mikefarah/yq
 ```
 
-Or, in your docker file:
+```
+podman run --user="root" -it --entrypoint sh mikefarah/yq
+```
+
+Or, in your Dockerfile:
 
 ```
 FROM mikefarah/yq