filemerge: when using in-memory merge, always put backup files in temp dir
Before calling a merge tool, we create a backup of the local side of
the merge. That file can be put in the working copy or in a temporary
directory, depending on the user's config. When we're merging in
memory, we don't want to write to the actual, on-disk working copy, so
we write the file to the in-memory working copy instead. However,
since we don't support external merge tools with in-memory merge, it
makes no difference where the file is actually stored (and if we ever
do add support for external merge tools, then the file clearly can't
live in the in-memory working-copy object anyway). So, since it
doesn't matter where the file is stored, we can simplify by always
putting them in the system's temp directory.
Differential Revision: https://phab.mercurial-scm.org/D12187
== New Features ==
* The amend extension supports the `--currentuser` argument.
* The amend extension supports the `--close-branch` argument.
* The amend extension supports the `--secret` argument.
* The uncommit extension supports the `rewrite.update-timestamp` config option.
== New Experimental Features ==
== Bug Fixes ==
== Backwards Compatibility Changes ==
* A shell that supports `$(command)`` syntax for command substitution is now
required for running the test suite. The test runner normally uses
`sh`, so if that is a shell that doesn't support `$(command)` syntax,
you can override it by setting `$HGTEST_SHELL` or by passing it to
`run-tests.py --shell <shell>`.
* The (experimental) narrow extension's wire protocol changed. If
you're using it, you'll need to make sure to upgrade server and
client at the same time.
== Internal API Changes ==