DOC: document how to skip CI jobs

This is a follow-up to gh-18333.

Self-test: docs get built on CircleCI, so let's skip the other
platforms:

[skip github]
[skip azurepipelines]
[skip appveyor]
[skip travis]

1 files changed, 22 insertions, 0 deletions

diff --git a/doc/source/dev/development_workflow.rst b/doc/source/dev/development_workflow.rst
index 8c56f6fb2..ce6ea3c7f 100644
--- a/doc/source/dev/development_workflow.rst
+++ b/doc/source/dev/development_workflow.rst
@@ -187,6 +187,28 @@ Standard acronyms to start the commit message with are::
    TST: addition or modification of tests
    REL: related to releasing numpy
 
+Commands to skip continuous integration
+```````````````````````````````````````
+
+By default a lot of continuous integration (CI) jobs are run for every PR,
+from running the test suite on different operating systems and hardware
+platforms to building the docs. In some cases you already know that CI isn't
+needed (or not all of it), for example if you work on CI config files, text in
+the README, or other files that aren't involved in regular build, test or docs
+sequences. In such cases you may explicitly skip CI by including one of these
+fragments in your commit message::
+
+   ``[ci skip]``: skip as much CI as possible (not all jobs can be skipped)
+   ``[skip github]``: skip GitHub Actions "build numpy and run tests" jobs
+   ``[skip travis]``: skip TravisCI jobs
+   ``[skip azurepipelines]``: skip Azure jobs
+   ``[skip appveyor]``: skip Appveyor jobs
+
+*Note: unfortunately not all CI systems implement this feature well, or at all.
+CircleCI supports ``ci skip`` but has no command to skip only CircleCI.
+Azure chooses to still run jobs with skip commands on PRs, the jobs only get
+skipped on merging to master.*
+
 
 .. _workflow_mailing_list: