Mercurial: update to a revision, but not modify local files

Question

Suppose the repository has 20 revisions. The current revision on the record is revision 10, while the actual local files are based on the latest revision 20. I do not want to branch from revision 10. I want to continue the revision 20.

Currently what I'm doing is to copy all the files out of the revision directory, run hg update -C (which updates the revision number), remove all the files in the repository directory, copy all the files back, then commit. You can tell this is annoying and time wasteful. Is there a way to only update the revision number, but not modify any local file?

Thanks in advance.

EDIT: there are many use cases (I mainly use TortoiseHg).

1) I mistakenly choose "No" when prompted to remove files from repository during a commit. I can use the strip from mq to remove the revision, but that will revert all commited files. Instead, I want to "re-parent" to the previous revision, commit again, then strip the unwanted revision. This may happen to anybody anytime, not just me, not just once.

2) I had a development machine A. I started the project on it, and switch to machine B after several months. The code on A becomes old, and the code on B has uncommited changed. If I want to continue development on A, I need to copy the code to A via Flash or network, etc. Now I want to commit on A without branching (because the code on A is actually based on the current tip). This happens maybe less frequently, but still not "once" problem, and more possibly when involved in a big project.

3) The repository has 2 branches C and D. There are roughly 2000 files. The current tip is in C. I want to overwrite some files in D with the same-named files in C (because C is more implemented) while preserving other files unchanged, then make the new tip in D. I have several options. I could update to D, compare the last revision of D with the current tip, make change and commit. The update would take some time, and the difficulty of comparison heavily relies on the comparison tool. I could also compare first, make change, backup the entire directory, update to D, then restore the entire directory. This is even more cumbersome. But if I could "re-parent" to D, I just need to make change and commit. This does not rely on comparison tool because the commit window in TortoiseHg has diff list.

There could be more use cases if you want to think. I hope Mercurial provides such "re-parent" feature (supposedly a new option for hg update), or at least convenient alternative.

Answer 1

You might find this article useful. The original link no longer exists, so it now references the Internet Archive's copy:

https://web.archive.org/web/20170805042314/http://hgtip.com/tips/advanced/2010-04-23-debug-command-tricks

In particular, to "reparent" your current working directory, issue:

hg debugsetparent 20
hg debugrebuildstate