Template strings in VERSION are likely to collide with real tags

[regularfry]

What is the problem this feature will solve?

Right now the template substitution done to the VERSION file uses short template strings composed only of letters. One of the goals of the tagging mechanism is that people should be able to use whatever static strings they like to tag images, but with letter-based template tags (especially if people want to name things after branches) we run into this situation:

fixed-hash-function-branch => fixed-1234abcd-function-branch
remove-comments => remove-co08ents
bug-ridden-no-more => bug-ri30en-no-more

...among other possible examples.

What is the feature that you are proposing to solve the problem?

We replace the use of yyyy/mm/dd template strings with date-format-style specifiers, implemented either explicitly, by substituting %Y/%m/%d-style template tags with sed as now, or implicitly, by passing the entire line through to date itself as a format string. In the latter case we'd need to come up with a way to handle git hashes and anything else we want to expose.

What alternatives have you considered?

No response

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[stefaniuk]

Good spot. Thanks. I propose we use the ${yyyy}${mm}${dd}${HH}${MM}${SS}-${hash} pattern instead of yyyymmddHHMMSS-hash. Therefore, the sed expressions change to:

cat "$dir/VERSION" | \
      sed "s/\${yyyy}/$(date --date="${build_datetime}" -u +"%Y")/g" | \
      sed "s/\${mm}/$(date --date="${build_datetime}" -u +"%m")/g" | \
      sed "s/\${dd}/$(date --date="${build_datetime}" -u +"%d")/g" | \
      sed "s/\${HH}/$(date --date="${build_datetime}" -u +"%H")/g" | \
      sed "s/\${MM}/$(date --date="${build_datetime}" -u +"%M")/g" | \
      sed "s/\${SS}/$(date --date="${build_datetime}" -u +"%S")/g" | \
      sed "s/\${hash}/$(git rev-parse --short HEAD)/g" \
    > "$dir/.version"

The ${variable} pattern used for substitution should be recognised by anyone who is familiar with shell/make scripting.

• This is going to be fixed as part of the PR #112

[regularfry]

That's probably fine, but there's a little voice in the back of my head saying that if it looks like shell variables we'll get people trying to use $yyyy without the brackets, and getting confused when that doesn't work. We could make the brackets optional?

[stefaniuk]

Added but not documented as the use of it is discouraged due to readability: ${yyyy}${mm}${dd} vs. $yyyy$mm$dd

[regularfry]

I like it, that's a pretty good tradeoff. We're not encouraging it but we're also not surprising someone whose muscle memory leaves off the brackets.