Add a scheduled workflow to synchronize branches from gitster/git

[dscho]

This ports over https://dev.azure.com/gitgitgadget/git/_build?definitionId=8 from an Azure Pipeline to a GitHub workflow.

[webstech]

Still in progress but I have to step away for a bit.

[webstech]

Maybe a little clearer on the increments?

              } else { // they are a match
               if (sourceRefs[i].object.sha !== targetRefs[j].object.sha) {
                  // target ref needs updating
                  const sha = sourceRefs[i].object.sha
                  toFetch.add(sha)
                  refspecs.push(`+${sha}:${sourceRefs[i].ref}`)
                } 
                i++
                j++
              }

[dscho]

Good point!

[dscho]

@webstech here is another iteration of this PR. Range-diff to what you reviewed:

• 1: 0627ed0 ! 1: f69d3e6 Add a scheduled workflow to synchronize branches from gitster/git

  @@ .github/workflows/sync-gitster-git.yml (new)
   +              const { data } = await github.rest.git.listMatchingRefs({
   +                owner,
   +                repo,
  ++                // We want to match `maint-*` as well as `[a-z][a-z]/*`
  ++                // sadly, this is not possible via GitHub's REST API,
  ++                // hence we do it below via the `filter()` call.
   +                ref: 'heads/'
   +              })
   +              return data
  @@ .github/workflows/sync-gitster-git.yml (new)
   +            const refspecs = []
   +            const toFetch = new Set()
   +            for (let i = 0, j = 0; i < sourceRefs.length || j < targetRefs.length; ) {
  -+              const c =  i >= sourceRefs.length
  ++              const compare =  i >= sourceRefs.length
   +                ? +1
   +                : j >= targetRefs.length
   +                  ? -1
   +                  : sourceRefs[i].ref.localeCompare(targetRefs[j].ref)
  -+              if (c > 0) {
  ++              if (compare > 0) {
   +                // no source ref => delete target ref
  -+                refspecs.push(`:${targetRefs[j++].ref}`)
  -+              } else if (c < 0) {
  ++                refspecs.push(`:${targetRefs[j].ref}`)
  ++                j++
  ++              } else if (compare < 0) {
   +                // no corresponding target ref yet => push source ref (new)
   +                const sha = sourceRefs[i].object.sha
   +                toFetch.add(sha)
  -+                refspecs.push(`${sha}:${sourceRefs[i++].ref}`)
  -+              } else if (c === 0 && sourceRefs[i].object.sha !== targetRefs[j].object.sha) {
  -+                // target ref needs updating
  -+                const sha = sourceRefs[i].object.sha
  -+                toFetch.add(sha)
  -+                refspecs.push(`+${sha}:${sourceRefs[i++].ref}`)
  -+                j++
  ++                refspecs.push(`${sha}:${sourceRefs[i].ref}`)
  ++                i++
   +              } else {
  ++                // the sourceRef's name matches the targetRef's
  ++                if (sourceRefs[i].object.sha !== targetRefs[j].object.sha) {
  ++                  // target ref needs updating
  ++                  const sha = sourceRefs[i].object.sha
  ++                  toFetch.add(sha)
  ++                  refspecs.push(`+${sha}:${sourceRefs[i].ref}`)
  ++                }
   +                i++
   +                j++
   +              }

• 2: e2422e2 ! 2: 1fabadb sync-gitster-git: handle 502 gracefully

  @@ .github/workflows/sync-gitster-git.yml: jobs:
   -              const { data } = await github.rest.git.listMatchingRefs({
   -                owner,
   -                repo,
  +-                // We want to match `maint-*` as well as `[a-z][a-z]/*`
  +-                // sadly, this is not possible via GitHub's REST API,
  +-                // hence we do it below via the `filter()` call.
   -                ref: 'heads/'
   -              })
   -              return data
   -                .filter(e => e.ref.match(/^refs\/heads\/(maint-\d|[a-z][a-z]\/)/))
   -                .sort((a, b) => a.ref.localeCompare(b.ref))
  -+              for (let i = 1; i <= 10; i++) {
  ++              let attemptCounter = 1
  ++              for (;;) {
   +                try {
   +                  const [owner, repo] = repository.split('/')
   +                  const { data } = await github.rest.git.listMatchingRefs({
   +                    owner,
   +                    repo,
  ++                    // We want to match `maint-*` as well as `[a-z][a-z]/*`
  ++                    // sadly, this is not possible via GitHub's REST API,
  ++                    // hence we do it below via the `filter()` call.
   +                    ref: 'heads/'
   +                  })
   +                  return data
  @@ .github/workflows/sync-gitster-git.yml: jobs:
   +                  if (e?.status !== 502) throw e
   +                }
   +
  -+                const seconds = i * i + 15 * Math.random()
  ++                if (++attemptCounter > 10) throw new Error('Giving up listing refs after 10 attempts')
  ++
  ++                const seconds = attemptCounter * attemptCounter + 15 * Math.random()
   +                core.info(`Encountered a Server Error; retrying in ${seconds} seconds`)
   +                await sleep(1000 * seconds)
   +              }

• -: ------- > 3: 525752b sync-gitster-git-branches: limit concurrency

[webstech]

Thanks.