+semver:patch does not seem to work with Mainline mode

[pshrosbree]

I do this:

λ gitversion /output json /showvariable SemVer
5.6.0

λ git commit -m "+semver:patch" --allow-empty
[develop 4e1b1bf5] +semver:patch

λ gitversion /output json /showvariable SemVer
5.6.0

Hmmm... maybe I need a merge another branch to get this effect, so:

λ gitversion /output json /showvariable SemVer
5.6.0

λ git checkout -B try-bump
Switched to a new branch 'try-bump'

λ git commit -m "+semver:patch" --allow-empty
[try-bump f532421a] +semver:patch

λ git checkout develop
Switched to branch 'develop'
Your branch is ahead of 'origin/develop' by 30 commits.
  (use "git push" to publish your local commits)

λ git merge try-bump
Updating 4e1b1bf5..f532421a
Fast-forward

λ gitversion /output json /showvariable SemVer
5.6.0

OK, let's add a commit on master:

λ git commit -m "+semver:patch" --allow-empty
[develop 63e0865c] +semver:patch

λ gitversion /output json /showvariable SemVer
5.6.0

So, why?

The GitVersion.yml is:

λ gitversion /showconfig
assembly-versioning-scheme: MajorMinorPatchTag
assembly-file-versioning-scheme: MajorMinorPatch
mode: Mainline
tag-prefix: '[vV]'
continuous-delivery-fallback-tag: ci
major-version-bump-message: '\+semver:\s?(breaking|major)'
minor-version-bump-message: '\+semver:\s?(feature|minor)'
patch-version-bump-message: '\+semver:\s?(fix|patch)'
no-bump-message: '\+semver:\s?(none|skip)'
legacy-semver-padding: 4
build-metadata-padding: 4
commits-since-version-source-padding: 4
commit-message-incrementing: Enabled
branches:
  master:
    mode: ContinuousDelivery
    tag: ''
    increment: Patch
    prevent-increment-of-merged-branch-version: false
    track-merge-target: false
    regex: develop
    tracks-release-branches: false
    is-release-branch: false
    is-mainline: true

If this is correct behavior, how do I get commits (merge or otherwise) on master (develop) to bump the patch version?

λ git log

commit 63e0865ce678fbe58f9f4b0daef9142466b06b81 (HEAD -> develop)
Author: Peter Shrosbree <petshr@microsoft.com>
Date:   Fri Sep 15 14:21:33 2017 -0700

    +semver:patch

commit f532421a043da18832c5c34eefb9856ca9bd387e (try-bump)
Author: Peter Shrosbree <petshr@microsoft.com>
Date:   Fri Sep 15 14:19:49 2017 -0700

    +semver:patch

commit 4e1b1bf5c5fd4f7afcb346f2882f62e8151375ac
Author: Peter Shrosbree <petshr@microsoft.com>
Date:   Fri Sep 15 14:18:09 2017 -0700

    +semver:patch

[pshrosbree]

After posting this I tried doing this on a branch called master with the same configuration as above, and it worked as expected. However, if I changed the configuration so that the master regex configuration setting is master, it goes back to the previously described (and unexpected by me) behaviour:

assembly-versioning-scheme: MajorMinorPatchTag
assembly-file-versioning-scheme: MajorMinorPatch
mode: Mainline
increment: Patch
commit-message-incrementing: Enabled
branches:
  master:
    mode: ContinuousDelivery
    tag: ''
    increment: Patch
    prevent-increment-of-merged-branch-version: false
    track-merge-target: false
    regex: master
    tracks-release-branches: false
    is-release-branch: false
    is-mainline: true

So it seems that I don't understand how to configure GitVersion.

Here is what we would like:

Everyone PRs their code to develop.
Once we're happy with what is on develop we merge it to the staging branch and test in staging.
Once we're happy with staging we merge it to the production branch and deploy.
We would like every commit or merge to develop to bump the patch version and honour any +semver: commit comments.
Note that there is no branch called master. Are we just calling master develop? If so, how do we configure that? Is it sufficient to set the master regex to develop?

How can this be achieved?

Using GitVersion 4.0.0-beta.12+1315.Branch.master.Sha.9c70946f68973b3b31b2861913c247fbe6c3f0ec

[pshrosbree]

I'll repeat this as a question about configuration.