Question

I think I already know the answer to this but thought I would ask anyway:

We have a file that got added to a Mercurial repository with sensitive information in it. Is there any way to remove that file along with its change history without removing the whole repo?

Answer 1

No, you can’t. Read the changes that should have never been section of the mercurial red book about it; and particularly the what about sensitive changes that escape subsection, which contains this paragraph:

Mercurial also does not provide a way
to make a file or changeset completely
disappear from history, because there
is no way to enforce its
disappearance; someone could easily
modify their copy of Mercurial to
ignore such directives. In addition,
even if Mercurial provided such a
capability, someone who simply hadn’t
pulled a “make this file disappear”
changeset wouldn’t be affected by it,
nor would web crawlers visiting at the
wrong time, disk backups, or other
mechanisms. Indeed, no distributed
revision control system can make data
reliably vanish. Providing the
illusion of such control could easily
give a false sense of security, and be
worse than not providing it at all.

The usual way to revert committed changes is supported by mercurial through the backout command (again, mercurial book: dealing with committed changes) but the information does not disappear from the repository: since you never know who exactly cloned your repository, that would give a false sense of security, as explained above.