It turns out that `--help` provides a longer version of the help text
than `-h` does. I only discovered that because I was wondering what
the difference between `clap::App::about()` and
`clap::App::long_about()` was. There's clap-rs/clap#1015 for tracking
it in clap, but let's clarify it ourselves for now by changing the
help text for `-h/--help`.
With this commit, you can run `jj concepts branches` to get help about
the "branches" concept. We don't have much help for other commands and
their arguments yet, but I'm starting with concept guides so we can
point to them as we add help for commands and their arguments.
I initially tried to make the command to get help be `jj help
--concept branches`. That would require replacing clap's
implementation of the help command with our own. clap-rs/clap#1350
prevented me from doing that. But I'm pretty happy with having it
under `jj concepts` anyway. It's probably more discoverable that way.
I tried to mimic clap's styling with yellow headings.
Clap uses present tense by default (e.g. "Prints help information"). I
considered switching our message to that style, but I found it harder
to describe some flags that way.
I think it makes sense to have a version of rebase that rebases the
descendants of the rebased commit onto the parents of the rebased
commit. Let's make `jj rebase -r` do just that. Let's also add `jj
rebase -s` (matching Mercurial's `hg rebase -s`) for rebasing a commit
and its descendants onto another commit.
Since both flavors of the command now explicitly rebase the
descendants (just to different destinations), I also made the command
not evolve orphans afterwards. That would have made sense regardless
of this commit.
This change makes `jj status` include a section about conflicted local
branches and another section about conflicted remote branches. They
show up only if there are conflicts. They include hints about how to
resolve.
The auto-rebasing of descendants doesn't work if you have an open
commit checked out, which means that you may still end up with orphans
in that case (though that's usually a short-lived problem since they
get rebased when you close the commit). I'm also about to make
branches update to successors, but that also doesn't work when the
branch is on a working copy commit that gets rewritten. To fix this
problem, I've decided to let the caller of `WorkingCopy::commit()`
responsible for the transaction.
I expect that some of the code that this change moves from the lib
crate to the cli crate will later move back into the lib crate in some
form.
I want to reuse this bit of code for evolving descendants of a
rewritten working copy commit.
I expect this to change again soon (I'll probably make it do a regular
rebase instead of evolve), but this will do for now.
This makes it so (local) branches get updated when the commit they
point to gets rewritten. If the branch was conflicted, we just print a
warning and don't update the branch (though one could imagine
rewriting the conflict). We also just print a warning if the new
target is unclear because the commit was rewritten into multiple new
commits (divergent).
The updating doesn't work when the working copy commit gets rewritten
because the working copy changed on disk. That's because that's done
in a separate transaction inside `working_copy.rs`. That's similar to
how orphans of the working copy commit don't get automatically
evolved. I'll fix both problems soon.
With this change, we no longer fail if the user moves a branch
sideways or backwards and then push.
The push should ideally only succeed if the remote branch is where we
thought it was (like `git push --force-with-lease`), but that requires
rust-lang/git2-rs#733 to be fixed first.
Now that we have native branches, we can make `jj git push` only be
about pushing a branch to a remote branch with the same name.
We may want to add back support for the more advanced case of pushing
an arbitrary commit to an arbitrary branch later, but let's get the
common case simplified first.
I had forgotten to make the `delete` argument a flag by giving it a
name, so instead it conflicted with `name` argument, as tests
discovered.
While at it, I also made `name` required. It wasn't before because I
originally had a single command for `jj branch` and `jj branches` and
then I didn't think to make it required when I split them up.
Now that our own branches and tags are updated when git refs are
updated and the user can use them to specify revisions, we can start
displaying them instead of the git refs. This commit adds new
`branches` and `tags` template keywords and updates the default
templates to use them instead of `git_refs`.
This adds support for having conflicting git refs in the view, but we
never create conflicts yet. The `git_refs()` revset includes all "add"
sides of any conflicts. Similarly `origin/main` (for example) resolves
to all "adds" if it's conflicted (meaning that `jj co origin/main` and
many other commands will error out if `origin/main` is
conflicted). The `git_refs` template renders the reference for all
"adds" and adds a "?" as suffix for conflicted refs.
The reason I'm adding this now is not because it's high priority on
its own (it's likely extremely uncommon to run two concurrent `jj git
refresh` and *also* update refs in the underlying git repo at the same
time) but because it's a building block for the branch support I've
planned (issue #21).
The new `diff::DiffHunk` type is very similar but more generic. We
don't need the generality here. I just don't two very similar types
with the same name.
This change teaches `Tree::diff()` to filter by a matcher. It only
filters the result so far; it does not restrict the tree walk to what
`Matcher::visit()` says is necessary yet. It also doesn't teach the
CLI to create a matcher and pass it in.
This patch makes it so we use color in the graph iff we use it other
output. We currently always use color except for in the smoke tests,
so it has no effect in practice. It's easy to turn off color when
stdout is redirected (using the `atty` crate), but I haven't done that
because I occasionally pipe `jj log` output to `less` and I want color
then.
This both helps find the current checkout and head operation and
hopefully helps teach the user that "@" is the symbol for the working
copy. I removed the current "<--" indication from the graph (and
non-graph) log template. Hopefully the "@" is clear enough on its own,
but we may want to add back some further indication later. We'll see.
I considered even changing the message to "Checking out: <commit>" as
that's technically more correct (the message is printed when the
view's checkout is updated, i.e. before the working copy is
updated). However, I worried that users would find it confusing that
e.g. `jj close` would result in a "Checking out: " message, even
though that's what actually happens.
I remember adding that message a long time ago so the user has a trace
of working copy commit ids in the terminal output. They should be able
to get the same information from the operation log combined with
e.g. `jj st --at-op`.
We already support using "@" to refer to the head operation when doing
e.g. `jj op undo -o @`. This patch adds support for `--at-op=@`. It
also makes that the default.
This prepares `jj status` for working better on an old repo state
(with `--at-op`). When looking at an old repo state, the "working
copy" should reflect the state from that state, i.e. the view's
"checkout", not the current working copy.
Before this patch, `jj log` would always commit the working copy and
most other commands would commit the working copy only if they were
passed a revset of exactly "@". This patch makes it so they all commit
the working copy unless they are passed just a symbol other than "@"
(typically a commit id). That means that we will not commit the
working copy if the user does `jj diff -r abc123`, but we will if they
do `jj diff -r :abc123`. It's clearly unnecessary in both those cases,
and we should fix, but this is probably good enough for now.
This patch adds checks in all (?) commands that rewrite commits to
make sure the commit they're about to rewrite is allowed to be
rewritten. The only check we do is that it's not a root commit. We
should at least add checks for public commits later.
Now that we auto-evolve after most operations, the user may not know
what "evolve" means. Even before that, the way `jj evolve` resolved
orphans after pruning was by rebasing them.
Perhaps it makes more sense to display the working copy commit just
above the changes in the working copy commit, even though that means
that the order between the working copy commit and the parent becomes
the opposite of the order in `jj log`.
I had initially hoped that the type-safety provided by the separate
`FileRepoPath` and `DirRepoPath` types would help prevent bugs. I'm
not sure if it has prevented any bugs so far. It has turned out that
there are more cases than I had hoped where it's unknown whether a
path is for a directory or a file. One such example is for the path of
a conflict. Since it can be conflict between a directory and a file,
it doesn't make sense to use either. Instead we end up with quite a
bit of conversion between the types. I feel like they are not worth
the extra complexity. This patch therefore starts simplifying it by
replacing uses of `FileRepoPath` by `RepoPath`. `DirRepoPath` is a
little more complicated because its string form ends with a '/'. I'll
address that in separate patches.
I thought I had looked for this case and cleaned up all the places
when I made `Transaction::commit()` return a new `ReadonlyRepo`. I
must have forgotten to do that, because there we tons of places to
clean up left.
If you ran two concurrent `jj describe` (for example) before this
patch, they'd both try to open an editor on the same file. This patch
fixes that by randomizing the filename. It also deletes the file at
the end so the `.jj/` directory is not cluttered by these files.
It's annoying to have to run run `jj evolve`, and it's easy to forget
(especially after updating the description of the working copy
parent), so let's just always do it. Unlike most VCSs, we don't have
to worry about merge conflicts since we can represent them in commits.
This commit rewites the divergence-resolution part of `evolve()` as an
iterator (though not implementing the `Iterator` trait). Iterators are
just much easier to work with: they can easily be stopped, and errors
are easy to propagate. This patch therefore lets us propagate errors
from writing to stdout (typically pipe errors).
When using the command line interface (which is the only interface so
far), it seems more useful to see the exact command that was run than
a logical description of what it does. This patch makes the CLI record
that information in the operation metadata in a new key/value field. I
put it in a generic key/value field instead of a more specialized
field because the key/value field seems like a useful thing to have in
general. However, that means that we "have to" do shell-escaping when
saving the data instead of leaving the data unescaped and adding the
shell-escaping when presenting it. I added very simple shell-escaping
for now.
Almost all commands should update the checkout after rewriting
commits, so this patch teaches the `RepoCommand` helper to take care
of that by default.
This patch introduces a type that keeps some state that is used by
commands that act on a repo (i.e. most commands). The short-term goal
with this refactoring is to use the new type for passing the full
list of command-line arguments as metadata on the transaction.
This patch on its own is a net increase in lines of code. Hopefully
that can be reversed with some further patches.
This commit adds support for defining command aliases. The aliases are
read from the `[alias]` section and are expected to be TOML arrays
with one element per argument.
When rendering a non-contiguous subset of the commits, we want to
still show the connections between the commits in the graph, even
though they're not directly connected. This commit introduces an
adaptor for the revset iterators that also yield the edges to show in
such a simplified graph.
This has no measurable impact on `jj log -r ,,v2.0.0` in the git.git
repo.
The output of `jj log -r 'v1.0.0 | v2.0.0'` now looks like this:
```
o e156455ea491 e156455ea491 gitster@pobox.com 2014-05-28 11:04:19.000 -07:00 refs/tags/v2.0.0
:\ Git 2.0
: ~
o c2f3bf071ee9 c2f3bf071ee9 junkio@cox.net 2005-12-21 00:01:00.000 -08:00 refs/tags/v1.0.0
~ GIT 1.0.0
```
Before this commit, it looked like this:
```
o e156455ea491 e156455ea491 gitster@pobox.com 2014-05-28 11:04:19.000 -07:00 refs/tags/v2.0.0
| Git 2.0
| o c2f3bf071ee9 c2f3bf071ee9 junkio@cox.net 2005-12-21 00:01:00.000 -08:00 refs/tags/v1.0.0
| |\ GIT 1.0.0
```
The output of `jj log -r 'git_refs()'` in the git.git repo is still
completely useless (it's >350k lines and >500MB of data). I think
that's because we don't filter out edges to ancestors that we have
transitive edges to. Mercurial also doesn't filter out such edges, but
Git (with `--simplify-by-decoration`) seems to filter them out. I'll
change it soon so we filter them out.
I've often missed not having the timestamp there. It gets too long
with both email and timestamp for both author and committer, so I
removed the committer email to make room for the author timestamp.
I really liked the idea of having the operators for parents and
ancestors (etc.) look similar, but that turned out to be problematic
when we want to add an infix operator for a DAG range (hg's `::`
revset operator and git's `--ancestry-path` flag). Let's say we chose
`:*:` as the operator. Part of the problem is how to parse `foo:*:bar`
without eagerly parsing the `foo:`. It would also be nicer to use
exactly the same operator as prefix, postfix, and infix. Since the
"parents" operator can be repeated, we can't have it be just `:` and
the "ancestors" operator be `::`. We could make the "ancestors"
operator be something like `*:*` (or anything symmetric with the `:`
symbol on the inside). However, at that point, the operator is getting
ugly and hard to type. Another option would be to use `:` for
ancestors and `::` for parents, but that is counterintuitive and get
annoying if you want to repeat it. So it seems that the best option is
to simply pick different symbols for parents/children and
ancestors/descendants/range.
This patch changes the ancestors/descendants operators to both be
`,,`. I'm not at all attached to that particular symbol. I suspect
we'll change it later.
This teaches `jj log` a new `-r` option with a default of
`*:non_obsolete_heads()`. It also removes the `--all` option since
that's not used very frequently and can now be achieved with `jj log
-r '*:all_heads()'`.
When removing uninteresting heads, we had a check for explicitly
keeping the checkout (working copy) commit. I'm pretty sure that is a
leftover from before we had the "pruned" flag on commits; the working
copy should never be pruned or obsolete.
This patch adds initial support for a DSL for specifying revisions
inspired by Mercurial's "revset" language. The initial support
includes prefix operators ":" (parents) and "*:" (ancestors) with
naive parsing of the revsets. Mercurial uses postfix operator "^" for
parent 1 just like Git does. It uses prefix operator "::" for
ancestors and the same operator as postfix operator for descendants. I
did it differently because I like the idea of using the same operator
as prefix/postfix depending on desired direction, so I wanted to apply
that to parents/children as well (and for
predecessors/successors). The "*" in the "*:" operator is copied from
regular expression syntax. Let's see how it works out. This is an
experimental VCS, after all.
I've updated the CLI to use the new revset support.
The implementation feels a little messy, but you have to start
somewhere...
I suspect that at least one reason that I didn't make
`MutableRepo::base_repo` by an `Arc<ReadonlyRepo>` before was that I
thought that that would mean that `start_transaction()` would need be
moved off of `ReadonlyRepo` so it can be given an
`&Arc<ReadonlyRepo>`, which would make it much less convenient to
use. It turns out that a `self` argument can actually be of type
`&Arc<ReadonlyRepo>`.
My recent fix to print context lines when there are less than 3 lines
of context wasn't enough; we should also print context lines when
there are exactly 3 lines of context :) I can't understand what the
`!context_before` condition was for, so I've just removed it. I guess
I'll notice soon if things look worse in some case.
With lots of callbacks replaced by iterators, we are now ready to
propagate most cases of `BrokenPipe` errors to the top-level
`dispatch()` function where it gets ignored and we exit with an error
code.
This is yet another step towards making it easy to propagate
`BrokenPipe` errors. The `jj diff` code (naturally) diffs two trees
and prints the diffs. If the printing fails, we shouldn't just crash
like we do today.
The new code is probably slower since it does more copying (the
callback got references to the `FileRepoPath` and `TreeValue`). I hope
that won't make a noticeable difference. At least `jj diff -r
334afbc76fbd --summary` didn't seem to get measurably slower.
The new `jj unsquash` command moves changes from a commit's parent
into the commit itself. It comes with a `--interactive` flag. The
command is probably most useful for moving changes from the working
copy's parent into the working copy but it can of course be used for
moving changes into any commit (from that commit's parent).
This updates `jj log` to walk the index for doing the topological
walk, which is much faster than walking the object graph. This speeds
up `jj log | head -1` in the git.git repo from ~1.9s to ~0.27s (most
of the remaining time is spent calculating the evolve state).
A consequence of walking the index instead is that the order of
commits in the output is by by generation number. That's nice in some
ways, but it also means that the newest commit isn't always at the
top.
When I recently changed the revision argument from being passed to
`-r` to being a positional argument, I accidentally made it
required. Let's restore the default of "@".
I keep forgetting to pass the `-r`. The command takes only a revision
as argument and it doesn't seem likely that we'll want to positional
arguments for filenames in the future either.
`Transaction` has a bunch of functions that are now simple
delegates. It probably makes sense to directly use a `&mut
MutableRepo` instead of `&mut Transaction` in most places. This patch
starts that migration.
I just changed my `~/.gitignore` and some tests started failing
because the working copy respects the user's `~/.gitignore`. We should
probably not depend on `$HOME` in the library crate. For now, this
patch just makes sure we set it to an arbitrary directory in the tests
where it matters.
This patch continues the work from the previous pathc. From this
patch, we no longer calculate the evolution state just because a
transaction starts. We still unnecessarily calculate it when adding a
commit within the transaction, however. I'll fix that next.
"{:?}" escapes `\` to `\\` for Windows paths. That breaks tests checking
paths without using "{:?}". Use PathBuf::display() in both commands and
tests to get consistent output.
This fixes test_init_local, test_init_git_internal, and
test_init_git_external on Windows.
It's sometimes useful to create a `RepoLoader` given an existing
`ReadonlyRepo`. We already do that in `ReadonlyRepo::reload()`. This
patch repurposes `ReadonlyRepo::reload()` for that.
This is yet another step towards making the `View` types
simpler. Perhaps we eventually won't need to wrap the types returned
from the `OpStore` at all.
I'd like to make `ReadonlyView` and `MutableView` focused on just the
state of the view (i.e. the set of heads, git refs, etc.). The
responsibility for managing the `.jj/view/op_heads/` directory should
be moved out of it. This prepares for that.
The only way to load the repo at a current operation (as with
`--at-op`) is currently to first load it at the head operation and
then call `reload()` on the repo. This patch makes it so we can load
the repo directly at the requested operation.
The index is now always kept up to date and it has functionality for
finding common ancestors, so let's use it! This should make merging
commits a little faster if their common ancestor is far away (which is
rare). It's probably much more important that the index-based
algorithm is more correct. Also, it returns multiple common ancestors
in the criss-cross case, which lets us do a recursive merge like git
does. I'm leaving the recursive merge for later, though.
We currently need to read the commit objects for finding common
ancestors. That can be very slow when the common ancestor is far back
in history. This patch adds a function for finding common ancestors
using the index instead.
Unlike the current algorithm, which only returns one common ancestor,
the new index-based one correctly handles criss-cross merges.
Here are some timings for finding the common ancestors in the git.git
repo:
| Without index | With Index |
| First run | Subsequent | First run | Subsequent |
v2.30.0-rc0 v2.30.0-rc1 | 5.68 ms | 5.94 us | 40.3 us | 4.77 us |
v2.25.4 v2.26.1 | 1.75 ms | 1.42 us | 13.8 ms | 4.29 ms |
v1.0.0 v2.0.0 | 492 ms | 2.79 ms | 23.4 ms | 6.41 ms |
Finding ancestors of v2.25.4 and v2.26.1 got much slower because the
new algorithm finds all common ancestors. Therefore, it also finds
v2.24.2, v2.23.2, v2.22.3, v2.21.2, v2.20.3, v2.19.4, v2.18.3, and
v2.17.4, which it then filters out because they're all ancestors of
v2.25.3.
Also note that the result was incorrect before, because the old
algorithm would return as soon as it had found a common ancestor, even
if it's not the latest common ancestor. For example, for the common
ancestor between v1.0.0 and v2.0.0, it returned an ancestor of v1.0.0
because it happened to get there by following some side branch that
led there more quickly.
The only place we currently need to find the common ancestor is when
merging trees, which we only do when the user runs `jj merge`, as well
as when operating on existing merge commits (e.g. to diff or rebase
them). That means that this change won't be very noticeable. However,
it's something we clearly want to do sooner or later, so we might as
well get it done.
The `StoreWrapper` currently caches all objects it returns. That lead
to e.g. `common_ancestors()` being very fast once all commits have
been read in. For example, in the git.git repo `jj bench
commonancestors` with v1.0.0 and v2.0.0 reports 2.8ms, but the first
iteration takes 480ms. This commit highlights such differences by
adding a printout of the time it took to run the timed routine the
first time.
I want to keep the index updated within the transaction. I tried doing
that by adding a `trait Index`, implemented by `ReadonlyIndex` and
`MutableIndex`. However, `ReadonlyRepo::index` is of type
`Mutex<Option<Arc<IndexFile>>>` (because it is lazily initialized),
and we cannot get a `&dyn Index` that lives long enough to be returned
from a `Repo::index()` from that. It seems the best solution is to
instead create an `Index` enum (instead of a trait), with one readonly
and one mutable variant. This commit starts the migration to that
design by replacing the `Repo` trait by an enum. I never intended for
there there to be more implementations of `Repo` than `ReadonlyRepo`
and `MutableRepo` anyway.
I'm about to add the argument to `jj merge` and `jj close` as
well. For those, I think `--description` would have made more sense
than `--text`, but I don't like the idea of having the short form be
`-d` (sounds too much like `--destination` or `--delete`). It's
unfortunate that `jj describe` set the "commit description" but the
argument is called "message". That still seems better than calling the
command `jj message`.
We want to be able to be able to do fast `.contains()` checks on the
result, so `Iterator` was a bad type. We probably should hide the
exact type (currently `HashSet` for both readonly and mutable views),
but we can do that later. I actually thought I'd want to use
`.contains()` for indiciting public-phase commits in the log output,
but of course want to also indicate ancestors as public. This still
seem like a step (mostly) in the right direction.
I think it's better to let the caller decide if the parents should be
added. One use case for removing a head is when fetching from a Git
remote where a branch has been rewritten. In that case, it's probably
the best user experience to remove the old head. With the current
semantics of `View::remove_head()`, we would need to walk up the graph
to find a commit that's an ancestor and for each commit we remove as
head, its parents get temporarily added as heads. It's much easier for
callers that want to add the parents as heads to do that.
They're rendered as a single string created by joining the refs by
spaces because we don't have any support in the template language for
rendering a list.
It was really annoying that the order kept changing as commits got
rewritten. Also, I prefer to see the latest commits at the top (like
Mercurial does it).
This commits makes it so that running commands outside a repo results
in an error message instead of a panic.
We still don't look for a `.jj/` directory in ancestors of the current
directory.
I often (try to) use the command for throwing away all working copy
changes. That currently results in a crash on
`submatches.values_of("paths").unwrap()`. Let's make it revert
everything by default instead, since that seems to be my
intuition. Unlike most VCS's, we have a backup of the working copy and
the user can simply do `jj op undo` if they realized it was a mistake.
I'm preparing to publish an early version before someone takes the
name(s) on crates.io. "jj" has been taken by a seemingly useless
project, but "jujube" and "jujube-lib" are still available, so let's
use those.
The `evolve` command had TODOs about making it update the checkout and
the working copy after evolving commits. I've been running into that
(being left on an obsolete commit) quite often while dogfooding, so
let's fix it.
Until recently, we didn't have support for `.gitignore` files. That
meant that editors (like Emacs) that leave backup files around were
annoying to use, because you'd have to manually remove the backup file
afterwards. For that reason, I had hard-coded the editor to be
`pico`. Now we have support for `.gitignore` files, so we can start
respecting the user's $EDITOR.
When you run e.g. `jj st` outside of a repo, it just
crashes. That'll probably give new users a bad impression, so I
was planning to improve error handling a bit. A good place to
start is by fixing the code I recently added (which obviously
should have been using `thiserror` from the beginning). That's
what this commit does.
Also, this is the first commit in this repo created with
Jujube! I've just started dogfooding it myself.
With this commit, you can do `jj git clone
https://github.com/martinvonz/jj jj` and such, which seems like a good
step towards making it easier to get started.
This adds `jj git fetch` for fetching from a git remote. There remote
has to be added in the underlying git repo if it doesn't already
exist. I think command will still be useful on typical small projects
with just a single remote on GitHub. With this and the `jj git push` I
added recently, I think I have enough for my most of my own
interaction with GitHub.
I didn't know about the Clap setting to print help if no subcommand
was given, so I had reimplemented that myself for the top-level
command. However, if the user did e.g. `jj git`, they'd get a
crash. This commit fixes that by turning on the setting.
The fact that no commits from the underlying Git repo were imported
when creating a new Jujube repo from it was quite surprising. This
commit finally fixes that.
It's annoying to have to have the Git repo and Jujube repo in separate
directories. This commit adds `jj init --git`, which creates a new
Jujube repo with an empty, bare git repo in `.jj/git/`. Hopefully the
`jj git` subcommands will eventually provide enough functionality for
working with the Git repo that the user won't have to use Git commands
directly. If they still do, they can run them from inside `.jj/git/`,
or create a new worktree based on that bare repo.
The implementation is quite straight-forward. One thing to note is
that I made `.jj/store` support relative paths to the Git repo. That's
mostly so the Jujube repo can be moved around freely.
This commit starts adding support for working with a Jujube repo's
underlyng Git repo (if there is one). It does so by adding a command
for pushing from the Git repo to a remote, so you can work with your
anonymous branches in Jujube and push to a remote Git repo without
having to switch repos and copy commit hashes.
For example, `jj git push origin main` will push to the "main" branch
on the remote called "origin". The remote name (such as "origin") is
resolved in that repo. Unlike most commands, it defaults to pushing
the working copy's parent, since it is probably a mistake to push a
working copy commit to a Git repo.
I plan to add more `jj git` subcommands later. There will probably be
at least a command (or several?) for making the Git repo's refs
available in the Jujube repo.
This is just a little refactoring to prepare for making `jj split` ask
the user for commit descriptions. It's not actually needed, but it
doesn't make logical sense for the function to be about editing the
description of a particular commit.
This adds `jj edit`, which lets the user edit the content changes in a
commit. It behaves similar to `jj restore` when restoring the parent
commit, except that it edits the change compared to the re-merged
parents if the commit is a merge commit.
Changes to the "before" side of the diff will have no effect, so let's
clarify that by marking it readonly. At least Meld checks the
permissions and shows in the UI that the left side is readonly.
This adds an interactive mode for `jj restore`. It works by first
creating two temporary directories with the contents of the subset of
files that differ between the two trees, and then letting the user
edit the directory representing the right/after side. This has some
advantages compared to the interactive modes in Git and Mercurial:
* It lets the user edit the final state as opposed to the diff itself
(depending on the diff tool, of course). I think most users find it
easier to edit the file contents than to edit the patch
format.
* It delegates the hard work to a tool that is already written (this
is a big advantage for an immature tool like Jujube, but it is not
an advantage from the user's point of view).
Almost all of the work in this commit went into adding a function that
takes two trees, lets the user edit the diff, and returns a new tree
id. I plan to reuse that function for other interactive commands. One
planned command is `jj edit`, which will let the user edit the changes
in a commit. `jj edit -r abc123` will be mostly about providing a more
intuitive name for `jj restore --source abc123^ --destination abc123`,
plus it will be different for merge commits (it will edit only the
changes in the merge commit). I also plan to add `jj split` by letting
the user edit the full diff, leaving only the parts that should go
into the first commit. Perhaps there will also be commands for moving
part of a commit out of or into a parent commit.
This removes one level of indirection, which is nice because it was
visible to the callers. The `Index` struct is now empty. The next step
is obviously to delete it (and perhaps rename `IndexFile` to `Index`
or `ReadonlyIndex`).
