This adds a line to `set --show`s output like
```
$PATH: originally inherited as |/home/alfa/.local/bin:/usr/local/sbin:/usr/local/bin:/usr/bin:/usr/bin/site_perl:/usr/bin/vendor_perl:/usr/bin/core_perl:/var/lib/flatpak/exports/bin|
```
to help with debugging.
Note that this means keeping an additional copy of the original
environment around. At most this would be one ARG_MAX's worth, which
is about 2M.
This is sort of slow because it's called hundreds of times.
We used to have a cache, introduced in ad9b4290e, but it was removed
in fee5a9125a because it had
false-positives.
So what we do, because the issue is that this is called hundreds of
times per-commandline, we cache it keyed on the commandline.
This speeds up `complete -C'git sta'` by a factor of 2.3x.
It's still useful without, for instance to implement a command that
takes no options, or to check min-args or max-args.
(technically no optspecs, no min/max args and --ignore-unknown does
nothing, but that's a very specific error that we don't need to forbid)
Fixes#9006
Commit ad9b4290e optimized git completions by adding a completion that would
run on every completion request, which allows to precompute data used by
other completion entries. Unfortunately, the completion entry is not run
when the commandline contains a flag like `git -C`. If we didn't
already load git.fish, we'd error. Additionally, we got false positive
completions for `git diff -c`.
So this hack was a very bad idea. We should optimize in another way.
This is simply an error in test setup. There's a limit to how far we
can isolate them from the system.
(it's possible new cmake versions close fds automatically since I
can't reproduce the original issue via `ninja test` or `make test`)
Fixes#9017
This lacks the tmux-256color terminfo entry, leading to spurious
warnings like
warning: Could not set up terminal. <= no check matches
warning: TERM environment variable set to \'tmux-256color\'. <= no check matches
warning: Check that this terminal type is supported on this system. <= no check matches
warning: Using fallback terminal type \'ansi\'. <= no check matches
Git's pathspec system is kind of annoying:
> A pathspec that begins with a colon : has special meaning. In the short form, the leading colon : is followed by zero or more "magic signature" letters (which optionally is terminated by another colon :), and the remainder is the pattern to match against the path. The "magic signature" consists of ASCII symbols that are neither alphanumeric, glob, regex special characters nor colon. The optional colon that terminates the "magic signature" can be omitted if the pattern begins with a character that does not belong to "magic signature" symbol set and is not a colon.
So if we complete `:/foo`, that "works" because "f" is alphanumeric
and so the "/" is the only magic character here.
If, however the filename starts with a magic character, that's used as
a magic signature.
So we do what the docs say and terminate the magic signature after the
"/" (which means "from the repo root").
Fixes#9004
This makes it so
1. The informative status can work without showing untracked
files (previously it was disabled if bash.showUntrackedFiles was
false)
2. If untrackedfiles isn't explicitly enabled, we use -uno, so git
doesn't have to scan all the files.
In a large repository (like the FreeBSD ports repo), this can improve
performance by a factor of 5 or up.
In b0084c3fc4, we refactored out event handlers get removed. But this
also caused us to remove "one-shot" handlers even if they have not yet
been fired. Fix this.
When switching this to use `git status`, I neglected to use the
correct definition of what a "dirty" and a "staged" change is.
So this now showed already staged files still as "dirty".
Fixes#8986
This makes it so `complete -c foo -n test1 -n test2` registers *both*
conditions, and when it comes time to check the candidate, tries both,
in that order. If any fails it stops, if all succeed the completion is offered.
The reason for this is that it helps with caching - we have a
condition cache, but conditions like
```fish
test (count (commandline -opc)) -ge 2; and contains -- (commandline -opc)[2] length
test (count (commandline -opc)) -ge 2; and contains -- (commandline -opc)[2] sub
```
defeats it pretty easily, because the cache only looks at the entire
script as a string - it can't tell that the first `test` is the same
in both.
So this means we separate it into
```fish
complete -f -c string -n "test (count (commandline -opc)) -ge 2; and contains -- (commandline -opc)[2] length" -s V -l visible -d "Use the visible width, excluding escape sequences"
+complete -f -c string -n "test (count (commandline -opc)) -ge 2" -n "contains -- (commandline -opc)[2] length" -s V -l visible -d "Use the visible width, excluding escape sequences"
```
which allows the `test` to be cached.
In tests, this improves performance for the string completions by 30%
by reducing all the redundant `test` calls.
The `git` completions can also greatly benefit from this.
This adds a path builtin to deal with paths.
It offers the following subcommands:
filter to go through a list of paths and only print the ones that pass some filter - exist, are a directory, have read permission, ...
is as a shortcut for filter -q to only return true if one of the paths passed the filter
basename, dirname and extension to print certain parts of the path
change-extension to change the extension to a different one (as a string operation)
normalize and resolve to canonicalize the paths in various flavors
sort to sort paths, also only using the basename or dirname as a key
The definition of "extension" here was carefully considered and should line up with how extensions are actually used - ~/.bashrc doesn't have an extension, but ~/.conf.d does (".d").
These subcommands all compose well - they can read from arguments or stdin (like string), they can use null-delimited input or output (input is autodetected - if a NULL happens in the first PATH_MAX bytes it switches automatically).
It is both a failglob exception (so like set if a glob passed to it fails it just doesn't get any arguments for it instead of triggering an error), and passes output to command substitution buffers explicitly split (like string split0) so newlines are easy to handle.
This would still remove non-existent paths, which isn't a strict
inversion and contradicts the docs.
Currently, to only allow paths that exist but don't pass a type check,
you'd have to filter twice:
path filter -Z foo bar | path filter -vfz
If a shortcut for this becomes necessary we can add it later.
This is now added to the two commands that definitely deal with
relative paths.
It doesn't work for e.g. `path basename`, because after removing the
dirname prepending a "./" doesn't refer to the same file, and the
basename is also expected to not contain any slashes.
Because we now count the extension including the ".", we print an
empty entry.
This makes e.g.
```fish
set -l base (path change-extension '' $somefile)
set -l ext (path extension $somefile)
echo $base$ext
```
reconstruct the filename, and makes it easier to deal with files with
no extension.
This means "../" components are cancelled out even after non-existent
paths or files.
(the alternative is to error out, but being able to say `path resolve
/path/to/file/../../` over `path resolve (path dirname
/path/to/file)/../../` seems worth it?)
Yeah, the macOS tests fail because it's started in /private/var... with a
$PWD of /var.... So resolve canonicalizes the path, which makes it no
longer match $PWD.
Simply use pwd -P
This just goes back until it finds an existent path, resolves that,
and adds the normalized rest on top.
So if you try
/bin/foo/bar////../baz
and /bin exists as a symlink to /usr/bin, it would resolve that, and
normalize the rest, giving
/usr/bin/foo/baz
(note: We might want to add this to realpath as well?)
This includes the "." in what `path extension` prints.
This allows distinguishing between an empty extension (just `.`) and a
non-existent extension (no `.` at all).
This adds a "path" builtin that can handle paths.
Implemented so far:
- "path filter PATHS", filters paths according to existence and optionally type and permissions
- "path base" and "path dir", run basename and dirname, respectively
- "path extension PATHS", prints the extension, if any
- "path strip-extension", prints the path without the extension
- "path normalize PATHS", normalizes paths - removing "/./" components
- and such.
- "path real", does realpath - i.e. normalizing *and* link resolution.
Some of these - base, dir, {strip-,}extension and normalize operate on the paths only as strings, so they handle nonexistent paths. filter and real ignore any nonexistent paths.
All output is split explicitly, so paths with newlines in them are
handled correctly. Alternatively, all subcommands have a "--null-input"/"-z" and "--null-output"/"-Z" option to handle null-terminated input and create null-terminated output. So
find . -print0 | path base -z
prints the basename of all files in the current directory,
recursively.
With "-Z" it also prints it null-separated.
(if stdout is going to a command substitution, we probably want to
skip this)
All subcommands also have a "-q"/"--quiet" flag that tells them to skip output. They return true "when something happened". For match/filter that's when a file passed, for "base"/"dir"/"extension"/"strip-extension" that's when something about the path *changed*.
Filtering
---------
`filter` supports all the file*types* `test` has - "dir", "file", "link", "block"..., as well as the permissions - "read", "write", "exec" and things like "suid".
It is missing the tty check and the check for the file being non-empty. The former is best done via `isatty`, the latter I don't think I've ever seen used.
There currently is no way to only get "real" files, i.e. ignore links pointing to files.
Examples
--------
> path real /bin///sh
/usr/bin/bash
> path extension foo.mp4
mp4
> path extension ~/.config
(nothing, because ".config" isn't an extension.)
This teaches `--on-signal SIGINT` (and by extension `trap cmd SIGINT`)
to work properly in scripts, not just interactively. Note any such
function will suppress the default behavior of exiting. Do this for
SIGTERM as well.
Like `set` and `read` before it, `eval` can be used to set variables,
and so it can't be shadowed by a function without loss of
functionality.
So this forbids it.
Incidentally, this means we will no longer try to autoload an
`eval.fish` file that's left over from an old version, which would
have helped with #8963.
Previously, running `fish_add_path /foo /foo` would result in /foo
being added to $PATH twice.
Now we check that it hasn't already been given, so we skip the
second (and any further) occurence.
This *might* be a bit faster running under TSAN, otherwise it takes >
400 seconds on Github Actions.
If this doesn't work we need to disable it for TSAN.
Curses variables like `enter_italics_mode` are secretly defined to
dereference through the `cur_term` variable. Be sure we do not read or
write these curses variables if cur_term is NULL. See #8873, #8875.
Add a regression test.
To recap, this means `&` in the middle of a word no longer
backgrounds.
So:
```fish
echo foo&bar # prints foo&bar
echo foo& bar # backgrounds an echo that prints "foo" and runs "bar"
```
This can no longer be changed. If "no-stderr-nocaret" is in
$fish_features it will simply be ignored.
The "^" redirection that was deprecated in fish 3.0 is now gone for good.
Note: For testing reasons, it can still be set _internally_ by running
"feature_flags_t::set". We simply shouldn't do that.
Prior to this change, if you tab-completed a token with a wildcard (glob), we
would invoke ordinary completions. Instead, expand the wildcard, replacing
the wildcard with the result of expansions. If the wildcard fails to expand,
flash the command line to signal an error and do not modify it.
Example:
> touch file(seq 4)
> echo file*<tab>
becomes:
> echo file1 file2 file3 file4
whereas before the tab would have just added a space.
Some things to note:
1. If the expansion would produce more than 256 items, we flash the command
line and do nothing, since it would make the commandline overfull.
2. The wildcard token can be brought back through Undo (ctrl-Z).
3. This only kicks in if the wildcard is in the "path component
containing the cursor." If the wildcard is in a previous component,
we continue using completions as normal.
Fixes#954.
When you do
```fish
set foo-bar baz
```
"foo-baz" isn't usable as a variable *name*. When you just say the
"variable" is invalid that could also be interpreted to be a special
type of variable or something.
String tokens are subdivided by command substitutions. Some syntax errors
can occur in the gap between two command substitutions. Make the caret point
to the start of that gap, instead of the token start.
When expanding command substitutions, we use a naïve way of detecting whether
the cmdsub has the optional leading dollar. We check if the last character was
a dollar, which breaks if it's an escaped dollar. We wrongly expand
\$(echo "") to the empty string. Fix this by checking if the dollar was escaped.
The parse_util_* functions have a bunch of output parameters. We should
return a parameter bag instead (I think I tried once and failed).
Given
set var a
echo "$var$(echo b)"
the double-quoted string is expanded right-to-left, so we construct an
intermediate "$varb". Since the variable "varb" is undefined, this wrongly
expands to the empty string (should be "ab"). Fix this by isolating the
expanded command substitution internally. We do the same when handling
unquoted command substitutions.
Fixes#8849
The read test is now failing on GitHub actions even though it passes on
my Mac. It may be due to differences in dd between these two
environments. Stop using dd and just use head.
The read.fish check has a test where it limits the amount of data passed to
`read` to 8192 bytes, and verifies that fish reads exactly that amount.
This check occasionally fails on the OBS builds; it's very hard to repro a
failure locally, but I finally did it.
The amount of data written is limited via `yes` and `dd`:
yes $line | dd bs=1024 count=(math "$fish_read_limit / 1024")
The bug is that `dd` outputs a fixed number of "blocks" where a block
corresponds to a single read. As `yes` and `dd` are running concurrently,
it may happen that `dd` performs a short read; this then counts as a single
block. So `dd` may output less than the desired amount of data.
This can be verified by removing the 2>/dev/null redirection; on a
successful run dd reports `8+0 records out`, on a failed run it reports
`7+1 records out` because one of the records was short.
Fix this by using `fullblock` so that dd will no longer count a short read
as a single block. `head` would probably be a simpler tool to use but we'll
do this for now.
Happily it's not a fish bug. No need to relnote it.
This was already apparently supposed to work, but didn't because we
just overrode errno again.
This now means that, if a correctly named candidate exists, we don't
start the command-not-found handler.
See #8804
This used to call exec_subshell, which has two issues:
1. It creates a command substitution block which shows up in a stack
trace
2. It does much more work than necessary
This removes a useless "in command substitution" from an error message
in an autoloaded file, and it speeds up autoloading a bit (not
measurable in actual benchmarks, but microbenchmarks are 2x).
Cancellation groups were meant to reflect the following idea: if you ran a
simple block:
begin
cmd1
cmd2
end
then under job control, cmd1 and cmd2 would get separate groups; however if
either exits due to SIGINT or SIGQUIT we also want to propagate that to the
outer block. So the outermost block and its interior jobs would share a
cancellation group. However this is more complex than necessary; it's
sufficient for the execution context to just store an int internally.
This ought not to affect anything user-visible.
* Implement fish_wcstod_underscores
* Add fish_wcstod_underscores unit tests
* Switch to using fish_wcstod_underscores in tinyexpr
* Add tests for math builtin underscore separator functionality
* Add documentation for underscore separators for math builtin
* Add a changelog entry for underscore numeric separators
We can't always read in chunks because we often can't bear to
overread:
```fish
echo foo\nbar | begin
read -l foo
read -l bar
end
```
needs to have the first read read `foo` and the second read `bar`. So
here we can only read one byte at a time.
However, when we are directly redirected:
```fish
echo foo | read foo
```
we can, because the data is only for us anyway. The stream will be
closed after, so anything not read just goes away. Nobody else is
there to read.
This dramatically speeds up `read` of long lines through a pipe. How
much depends on the length of the line.
With lines of 5000 characters it's about 15x, with lines of 50
characters about 2x, lines of 5 characters about 1.07x.
See #8542.
This is the simple fix - if we have no valid digit, we have nothing to
return. So instead of returning a NULL, we return an error.
This is already the case for invalid octal escapes (like `\777`).
Fixes#8545
This reverts commits:
2d9e51b43ed1d9f147ec346ce8081b
The box drawing because it's entangled with the rest and we don't
currently use this anywhere I know of. Nor was it gated on terminfo,
so it could have broken things, for subjectively little gain.
Fixes#8727.
A history search ends when you move the cursor, but the commandline inserted by
history search is still marked as transient. This means that the next history
search will clear the transient commandline. This means we are dropping an undo
point, for example:
echo 11
echo 1
echo autosuggestion
echo^P # commandline is "echo 1"
^A # stop history search
^P # commandline is "echo 11"
^Z # Bug: commandline goes back to "echo", but it should be "echo 1"
In the worst case, we are switching from line-search to token-search (see
the attached test case). Clearing the transient edit means the line is gone
and only the token is left on the command line.
Say the user has a multi-char binding (typically an escape sequence), and a
signal arrives partway through the binding. The signal has an event handler
which enques some readline event, for example, `repaint`. Prior to this
change, the readline event would cause the multi-char binding to fail. This
would cause bits of the escape sequence to be printed to the screen.
Fix this by noticing when a sequence was "interrupted" by a non-char event,
and then rotating a sequence of such interruptions to the front of the
queue.
Fixes#8628
Today, a command like "var=val status " has custom completions
because we skip over the var=val variable override when detecting
the command token.
However if the custom completions read the commandline state (via
"commandline -opc") they do see they variable override, which breaks
them, most likely. Try "a=b git ".
For completions of wrapped commands, we already set a transient
commandline. Do the same for commands with leading variable overrides;
then git completions for "a=b git " will think the commandline is
"git ".
`read` allows specifying the initial command line text. This was
text got accidentally ignored starting in a32248277f. Fix this
regression and add a test.
Fixes#8633
Previously, when we got an unknown option with --ignore-unknown, we
would increment woptind but still try to read the same contents.
This means in e.g.
```
argparse -i h -- -ooo -h
```
The `-h` would also be skipped as an option, because after the first
`-o` getopt reads the other two `-o` and skips that many options.
This could be handled more extensively in wgetopt, but the simpler fix
is to just skip to the next argv entry once we have an unknown option
- there's nothing more we can do with it anyway!
Additionally, document this and clearly explain that we currently
don't transform the option.
Fixes#8637
fish_git_prompt may run certain git commands which may invoke certain
external programs as specified `.git/config`. Prevent this by suppressing
certain git config options.
This affects the caret position. In an expression like
123 456
we previously reported:
123 456
^ missing operator
Now we do:
123 456
^ missing operator
We do it on the first space, which should be acceptable.
(no need for a changelog entry, we have already ignored #8511)
Only show the shebang warning for .fish commands.
Use the phrase "interpreter directive" as the formal name for the
shebang.
Switch from windows to Windows for the operating system.
"not not return 34" exits with 34, not 1. This behavior is pretty
surprising but benign. I think it's very unlikely that anyone relies
on the opposite behavior, because using two "not" decorators in one
job is weird, and code that compares not's raw exit code is rare.
The behavior doesn't match our docs, but it's not worth changing the
docs because that would confuse newcomers. Add a test to cement the
behavior and a comment to explain this is intentional.
I considered adding the comment at
parse_execution_context_t::populate_not_process where this behavior
is implemented but the field defintion seems even better, because I
expect programmers to read that first.
Closes#8377
Commit e40eba358 (Treat text following quoted command substitution
as quoted) made parse_util_locate_cmdsubst_range() aware of quoted
command substitutions, by skipping surrounding text via quote_end().
However, it was not quite right. We fail to properly parse
two consecutive command substitutions in the same string,
because we don't maintain the quoting context across calls to
parse_util_locate_cmdsubst_range(). Let's track that bit in a
parameter. This allows us to get rid of the quote_end() hack.
Also apply this to the other place where we call
parse_util_locate_cmdsubst_range() in a loop (highlighting).
Fixes#8500
This fixes a regression about where we report errors:
echo error(here
old: ^
fixed: ^
Commit 0c22f67bd (Remove the old parser bits, 2020-07-02) removed
uses of "error_offset_within_token" so we always report errors at
token start. Add it back, hopefully restoring the 3.1.2 behavior.
Note that for cases like
echo "$("
we report "unbalanced quotes" because we treat the $( as double
quote. Giving a better error seems hard because of the ambguity -
we don't know if quote is meant to be inside or outside the command
substitution.
If you make a script called `foo` somewhere in $PATH, and did not give
it a shebang, this would end up calling
sh foo
instead of
sh /usr/bin/foo
which might not match up.
Especially if the path is e.g. `--version` or `-` that would end up
being misinterpreted *by sh*.
So instead we simply pass the actual_cmd to sh, because we need it
anyway to get it to fail to execute before.
For some reason, the window dimension parameters are ignored by tmux.
Not even an extra "resize-pane -x 80 -y 10" helps. So let's just drop
that assumption from our tests.
When the completion pager fills up all lines of the screen, we subtract
from the pager size the number of lines occupied by the prompt +
command line buffer (typically 1), so the command line is always
visible. However, we only subtract the number of lines *before* the
cursor, so on some multiline commandlines we draw a pager that is
too large for our screen, clobbering the commandline rendering.
Fix this by counting all lines.
Fixes#8509
Possibly fixes#8405
A command like "printf nonewline | sed s/x/y/" does not print a
concluding newline, whereas "printf nnl | string replace x y" does.
This is an edge case -- usually the user input does have a newline at
the end -- but it seems still better for this command to just forward
the user's data.
Teach most string subcommands to check if stdin is missing the trailing
newline, and stop adding one in that case.
This does not apply when input is read from commandline arguments.
* Most subcommands stop adding the final newline, because they don't
really care about newlines, so besides their normal processing,
they just want to preserve user input. They are:
* string collect
* string escape/unescape
* string join¹
* string lower/upper
* string pad
* string replace
* string repeat
* string sub
* string trim
* string match keeps adding the newline, following "grep". Additionally,
for string match --regex, it's important to output capture groups
separated by newlines, resulting in multiple output lines for an
input line. So it is not obvious where to leave out the newline.
* string split/split0 keep adding the newline for the same reason --
they are meant to output multiple elements for a single input line.
¹) string join0 is not changed because it already printed a trailing
zero byte instead of the trailing newline. This is consistent
with other tools like "find -print0".
Closes#3847
A «complete -C '~/fish-shell/build/fish '» fails to load custom
completions because we do not expand the ~, so
complete_param_for_command() thinks that this command is invalid.
Expand command tokens before loading custom completions.
Fixes#8442
Currently,
set -q --unpath PATH
simply ignores the "--unpath" bit (and same for "--path").
This changes it, so just like exportedness you can check pathness.
* fish_key_reader: Simplify default output
It now only prints the bind statement. Timing information and such is
relegated to a separate "verbose" mode.
* Adjust fish_key_reader docs
* Adjust tests
This finds the first broken component, to help people figure out where
they misspelt something.
E.g.
```
echo foo >/usr/lob/systemd/system/machines.target.wants/var-lib-machines.mount
```
will now show:
```
warning: Path '/usr/lob' does not exist
```
which would help with seeing that it should be "/usr/lib".
On a commandline like "ls arg" (cursor at end) we do not expand
abbrevations on enter. OTOH, on "ls " we do expand. This can be
frustrating because it means that the two obvious ways to suppress
abbrevation expansion (C-Space or post-expansion C-Z) cannot be used to
suppress expansion of a command without arguments. (One workaround is
"ls #".)
Only expand-on-execute if the cursor is at the command name (no space
in between).
This is a strict improvement for realistic scenarios, because if there
is a space, the user has already expressed the intent to not expand
the abbreviation. (I hope no one is using recursive abbreviations.)
Closes#8423
This was supposed to act like `type -q` or `command -q`, in that it
returns 0 if at least 1 exists.
But because it used the wrong variable it didn't.
Fixes#8431.
This allows rebinding escape in the user list without breaking e.g.
arrow keys (which send escape and then `[A` and similar, so escape is
a prefix of them).
Fixes#8428.
This fixes printing octal and hex values that are negative or larger
than UINT_MAX.
Negative values get a leading -, like:
> math --base hex -10
-0xa
Fixes#8417.
Commit ec3d3a481 (Support "$(cmd)" command substitution without line
splitting, 2021-07-02) started treating an input string like
"a$()b" as if it were "a"$()"b". Yet, we do not actually insert the
virtual quotes. Instead we just adapted the definition of when quotes
are closed - hence the changes to quote_end().
parse_util_locate_cmdsubst_range() is aware
of the changes to quote_end() but some of its
callers like parse_util_detect_errors_in_argument() and
highlighter_t::color_as_argument() are not. They split strings at
command substitution boundaries without handling the special quoting
rules. (Only the expansion logic did it right.)
Fix this by handling the special quoting rules inside
parse_util_locate_cmdsubst_range(). This is a bit hacky since it
makes it harder for callers to process some substrings in between
command substitutions, but that's okay because current callers only
care about what's inside the command substitutions.
Fixes#8394
Since #4376, for-loops would set the loop variable outside, so it
stays valid.
They did this by doing the equivalent of
```fish
set -l foo $foo
for foo in 1 2 3
```
And that first imaginary `set -l` would also fire a set-event.
Since there's no use for it and the variable isn't actually set, we
remove it.
Fixes#8384.
widechar_width no longer classifies U+1F41F as widened-in-9, so the
width no longer changes.
Since we're interested in testing the change here, we need a different
emoji.
Just use 🥁, which was introduced in 9 as wide, and therefore widened
in 9.
fish might use XDG_RUNTIME_DIR for the uvar notifier fifo, so this
makes sure that tests are isolated.
Also set permissions to comply with the XDG basedir spec.
Like the $status commit, this would add the offset to already existing
errors, so
```fish
(foo)
(bar)
something
```
would see the "(foo)" error, store the correct error location, then
see the "(bar)" error, and *add the offset of (bar)* to the "(foo)"
error location.
Solve this by making a new error list and appending it to the existing
ones.
There's a few other ways to solve this, including:
- Stopping after the first error (we only display the first anyway, I
think?)
- Making it so the source location has an "absolute" flag that shows
the offset has already been added (but do we ever need to add two offsets?)
I went with the simpler fix.
This would break the location of any prior errors without doing
anything of value.
E.g.
```fish
echo foo | exec grep # this exec is not allowed!
$status
somethingelse # The error might be found here!
```
Would apply the offset of `$status` to the offset of `exec`, locating
the error for `exec` somewhere after $status!
Prior to this change, tmux based tests would call 'isolated-tmux' which would
initialize tmux on first call, an admitted "evil hack." Switch to requiring
an explicit call to 'isolated-tmux-start' which then defines 'isolated-tmux'
and other functions. Add some loop-until-prompt logic into
'isolated-tmux-start'. This improves reliability of the tmux tests on systems
under load; at least it makes the tests pass in the background on my Mac.
Remove the '$sleep' variable, to be replaced with 'tmux-sleep'.
This makes it so we treat backspaces as width -1, but never go below a
0 total width when talking about *lines*, like in screen or string
length --visible.
Fixes#8277.
