See what is making a revision immutable

[jennings]

I have a revision that is immutable. How can I see what is making it immutable?

[jennings]

Revisions are immutable if it has a descendant in immutable_heads(). So, if you have an immutable revision REV, there must be an immutable head somewhere in REV::.

You can see what's making it immutable with the following command:

jj log -r 'REV | roots(REV:: & immutable_heads())'

Explaining this revset from the beginning:

Revset expression                       Explanation
--------------------------------------  --------------------------------------------------------------
            REV::                       Include a revision and all its descendants...

            REV:: & immutable_heads()   ...which are immutable heads

      roots(REV:: & immutable_heads())  Only show the "first" immutable head in a line of descendants

REV | roots(REV:: & immutable_heads())  Include REV, so the output shows the lineage between
                                        REV and the revisions making it immutable

You can make this a revset alias to make it reusable:

[revset-aliases]
'why_immutable(r)' = 'r | roots(r:: & immutable_heads())'

$ jj log -r 'why_immutable(xyz)'

[joyously]

This explanation should be in the FAQ or the revset page.
And perhaps a built-in alias.

[hotsphink]

I like it! I'd prefer (r & immutable()) | roots(r:: & immutable_heads()) so that it outputs nothing if r is in fact mutable.

[arxanas]

In general, it would be great to have a tool that walks through the evaluation of a revset to explain why a certain revision is or is not a member of each sub-term. I often needed to debug stuff when working on my perfect default log config, and it would have saved a lot of time if I knew exactly which function/operator was including/excluding the commit I wanted. (I think I often get confused by the exact behavior of .., for example.)