tools: forcefully build without manifest checking

[reliveyy]

This PR adds option -f and --force to tools/build command.

The redundant image pulling and tagging are also removed in this PR. See https://github.com/ExchangeUnion/xud-docker/pull/546/files#diff-8a792fef7c99bb820b9a2bbfe2d0d532L207-L212

[raladev]

if I understand correctly it should work in following way:

• tools/build - check image existing in docker hub for each image -> exists (if it does not exist, do nothing) -> check sum of image -> build new if sum is old OR just tag pulled image
• tools/build arby:latest - check image existing in docker hub -> exists (if it does not exist, move to build step) -> check sum of image -> build new if sum is old OR just tag pulled image
• tools/build -f arby:latest - build the tag w/o any checks

For now:

• tools/build returns nothing if there is no images in docker hub. (for example, when new branch in xud-docker is used). Solution: add output about docker hub checking and result of checking (no images in docker hub for this branch -> do nothing for tools/build call OR build image for tools/build arby call / image found, move to pulling);
• no output for docker hub checking and result of checking as a result there is no difference between tools/build arby:latest and tools/build arby:latest -f for new branch. Solution: add info about image pulling step + info about skipping because of -f flag;
• No use cases and examples for build/tools in README instead of tools/build. Difference in behavior of tools/build and tools/build arby confuses (for second one image will be built), so update of README is required + add info about force flag for tools/build arby -f case (because the flag does not work for tools/build -f call).

[reliveyy]

tools/build - check image existing in docker hub for each image -> exists (if it does not exist, do nothing) -> check sum of image -> build new if sum is old OR just tag pulled image

tools/build -> parse local git history and detect modifed images (details) -> check image with dockerhub registry -> missing or outdated -> real build

So tools/build may not interate over all images.

add output about docker hub checking and result of checking

FYI, you could inspect more details inside tools/tools.log. I used to print the details of modified images detection and dockerhub checking on the screen. But later I found out that I seldom look into these messages. So I think it is mainly used for debugging. Then I delete these messages to keep the build output clean recently.

But it is open to discuss of adding more details about the build like:

• No images changed in current branch
• Checking the existence of ... manifest on DockerHub registry
• Checking if the mainfest is up-to-date

BTW, if the build is skipped, a message will be printed in this PR:

Image is up-to-date. Skip building.

there is no difference between tools/build arby:latest and tools/build arby:latest -f for new branch

As I said above, you could find the differences in tools/tools.log. And besides the log file, tools/build -f is a little bit faster than tools/build.

No use cases and examples for build/tools in README instead of tools/build

Indeed. I'll add help docs about tools/build, tools/push, tools/test command later in another PR. And I add this PR only because I need to test #549 locally. If I run tools/build without -f then I will always get build command skipped locally.

add info about force flag for tools/build arby -f case (because the flag does not work for tools/build -f call).

I didn't get it why -f doesn't work in your case. Or is it just because there is no remarkable output text differences? @raladev

[raladev]

Q: What is the behaviour of tools/build -f for new branch in xud-docker repo?
A (from @reliveyy): What images to build for this command based on modified images detection. So could be nothing or something.
But -f option will skip the dockerhub manifest checking (for existence and version) for all the images from modified images detection