Commit Graph

97245 Commits

Author SHA1 Message Date
Johannes Schindelin
573dbb132b Merge remote-tracking branch 'dscho/add-p' into add-p-g4w
Let's test this for a while.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
2019-05-13 22:56:36 +02:00
Johannes Schindelin
b279b3a1b2 Merge branch 'stash-p-corner-case'
This topic branch fixes a corner case that is amazingly common in this
developer's workflow: in a `git stash -p`, splitting a hunk and stashing
only part of it runs into a (known) bug where the partial hunk cannot be
applied in reverse.

It is one of those "good enough" fixes, not a full fix, though, as the
full fix would require a 3-way merge between `stash^` and the *worktree*
(not `HEAD`), with `stash` as merge base (i.e. a `git revert`, but on
top of the current worktree).

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
2019-05-13 22:56:28 +02:00
Johannes Schindelin
e5f6204b71 Merge branch 'add-p-in-c-config-settings'
This is the final leg of the journey to a fully built-in `git add`: the
`git add -i` and `git add -p` modes were re-implemented in C, but they
lacked support for a couple of config settings.

The one that sticks out most is the `interactive.singleKey` setting: it
was not only particularly hard to get to work, especially on Windows. It
is also the setting that seems to be incomplete already in the Perl
version: while the name suggests that it applies to the main loop of
`git add --interactive`, or to the file selections in that command, it
does not. Only the `git add --patch` mode respects that setting.

As it is outside the purpose of the conversion of
`git-add--interactive.perl` to C, we will leave that loose end for some
future date.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
2019-05-13 22:56:28 +02:00
Johannes Schindelin
10b1eb3538 stash -p: (partially) fix bug concerning split hunks
When trying to stash part of the worktree changes by splitting a hunk
and then only partially accepting the split bits and pieces, the user
is presented with a rather cryptic error:

	error: patch failed: <file>:<line>
	error: test: patch does not apply
	Cannot remove worktree changes

and the command would fail to stash the desired parts of the worktree
changes (even if the `stash` ref was actually updated correctly).

We even have a test case demonstrating that failure, carrying it for
four years already.

The explanation: when splitting a hunk, the changed lines are no longer
separated by more than 3 lines (which is the amount of context lines
Git's diffs use by default), but less than that. So when staging only
part of the diff hunk for stashing, the resulting diff that we want to
apply to the worktree in reverse will contain those changes to be
dropped surrounded by three context lines, but since the diff is
relative to HEAD rather than to the worktree, these context lines will
not match.

Example time. Let's assume that the file README contains these lines:

	We
	the
	people

and the worktree added some lines so that it contains these lines
instead:

	We
	are
	the
	kind
	people

and the user tries to stash the line containing "are", then the command
will internally stage this line to a temporary index file and try to
revert the diff between HEAD and that index file. The diff hunk that
`git stash` tries to revert will look somewhat like this:

	@@ -1776,3 +1776,4
	 We
	+are
	 the
	 people

It is obvious, now, that the trailing context lines overlap with the
part of the original diff hunk that the user did *not* want to stash.

Keeping in mind that context lines in diffs serve the primary purpose of
finding the exact location when the diff does not apply precisely (but
when the exact line number in the file to be patched differs from the
line number indicated in the diff), we work around this by reducing the
amount of context lines: the diff was just generated.

Note: this is not a *full* fix for the issue. Just as demonstrated in
t3701's 'add -p works with pathological context lines' test case, there
are ambiguities in the diff format. It is very rare in practice, of
course, to encounter such repeated lines.

The full solution for such cases would be to replace the approach of
generating a diff from the stash and then applying it in reverse by
emulating `git revert` (i.e. doing a 3-way merge). However, in `git
stash -p` it would not apply to `HEAD` but instead to the worktree,
which makes this non-trivial to implement as long as we also maintain a
scripted version of `add -i`.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
2019-05-13 22:56:28 +02:00
Johannes Schindelin
67bcd45de1 Merge branch 'other-command-p-in-c'
At this stage on the journey to a fully built-in `git add`, we already
have everything we need, including the `--interactive` and `--patch`
options, as long as the `add.interactive.useBuiltin` setting is set to
`true` (kind of a "turned off feature flag", which it will be for a
while, until we get confident enough that the built-in version does the
job, and retire the Perl script).

However, the internal `add--interactive` helper is also used to back the
`--patch` option of `git stash`, `git reset` and `git checkout`.

This patch series brings them "online".

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
2019-05-13 22:56:28 +02:00
Johannes Schindelin
e8650dcef5 ci: include the built-in git add -i in the linux-gcc job
This job runs the test suite twice, once in regular mode, and once with
a whole slew of `GIT_TEST_*` variables set.

Now that the built-in version of `git add --interactive` is
feature-complete, let's also throw `GIT_TEST_MULTI_PACK_INDEX` into that
fray.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
2019-05-13 22:56:27 +02:00
Johannes Schindelin
01f25b9d01 t3904: fix incorrect demonstration of a bug
In 7e9e048661 (stash -p: demonstrate failure of split with mixed y/n,
2015-04-16), a regression test for a known breakage that was added to
the test script `t3904-stash-patch.sh` that demonstrated that splitting
a hunk and trying to stash only part of that split hunk fails (but
shouldn't).

As expected, it still fails, but for the wrong reason: once the bug is
fixed, we would expect stderr to show nothing, yet the regression test
expects stderr to show something.

Let's fix that by telling that regression test case to expect nothing to
be printed to stderr.

While at it, also drop the obvious left-over from debugging where the
regression test did not mind `git stash -p` to return a non-zero exit
status.

Of course, the regression test still fails, but this time for the
correct reason.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
2019-05-13 22:56:27 +02:00
Johannes Schindelin
7e033a8853 built-in stash: use the built-in git add -p if so configured
The scripted version of `git stash` called directly into the Perl script
`git-add--interactive.perl`, and this was faithfully converted to C.

However, we have a much better way to do this now: call `git add
--patch=<mode>`, which incidentally also respects the config setting
`add.interactive.useBuiltin`.

Let's do this.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
2019-05-13 22:56:27 +02:00
Johannes Schindelin
f22d698853 built-in add -p: handle Escape sequences more efficiently
When `interactive.singlekey = true`, we react immediately to keystrokes,
even to Escape sequences (e.g. when pressing a cursor key).

The problem with Escape sequences is that we do not really know when
they are done, and as a heuristic we poll standard input for half a
second to make sure that we got all of it.

While waiting half a second is not asking for a whole lot, it can become
quite annoying over time, therefore with this patch, we read the
terminal capabilities (if available) and extract known Escape sequences
from there, then stop polling immediately when we detected that the user
pressed a key that generated such a known sequence.

This recapitulates the remaining part of b5cc003253 (add -i: ignore
terminal escape sequences, 2011-05-17).

Note: We do *not* query the terminal capabilities directly. That would
either require a lot of platform-specific code, or it would require
linking to a library such as ncurses.

Linking to a library in the built-ins is something we try very hard to
avoid (we even kicked the libcurl dependency to a non-built-in remote
helper, just to shave off a tiny fraction of a second from Git's startup
time). And the platform-specific code would be a maintenance nightmare.

Even worse: in Git for Windows' case, we would need to query MSYS2
pseudo terminals, which `git.exe` simply cannot do (because it is
intentionally *not* an MSYS2 program).

To address this, we simply spawn `infocmp -L -1` and parse its output
(which works even in Git for Windows, because that helper is included in
the end-user facing installations).

This is done only once, as in the Perl version, but it is done only when
the first Escape sequence is encountered, not upon startup of `git add
-i`; This saves on startup time, yet makes reacting to the first Escape
sequence slightly more sluggish. But it allows us to keep the
terminal-related code encapsulated in the `compat/terminal.c` file.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
2019-05-13 22:56:27 +02:00
Johannes Schindelin
c4832c4af3 built-in add -p: handle Escape sequences in interactive.singlekey mode
This recapitulates part of b5cc003253 (add -i: ignore terminal escape
sequences, 2011-05-17):

    add -i: ignore terminal escape sequences

    On the author's terminal, the up-arrow input sequence is ^[[A, and
    thus fat-fingering an up-arrow into 'git checkout -p' is quite
    dangerous: git-add--interactive.perl will ignore the ^[ and [
    characters and happily treat A as "discard everything".

    As a band-aid fix, use Term::Cap to get all terminal capabilities.
    Then use the heuristic that any capability value that starts with ^[
    (i.e., \e in perl) must be a key input sequence.  Finally, given an
    input that starts with ^[, read more characters until we have read a
    full escape sequence, then return that to the caller.  We use a
    timeout of 0.5 seconds on the subsequent reads to avoid getting stuck
    if the user actually input a lone ^[.

    Since none of the currently recognized keys start with ^[, the net
    result is that the sequence as a whole will be ignored and the help
    displayed.

Note that we leave part for later which uses "Term::Cap to get all
terminal capabilities", for several reasons:

1. it is actually not really necessary, as the timeout of 0.5 seconds
   should be plenty sufficient to catch Escape sequences,

2. it is cleaner to keep the change to special-case Escape sequences
   separate from the change that reads all terminal capabilities to
   speed things up, and

3. in practice, relying on the terminal capabilities is a bit overrated,
   as the information could be incomplete, or plain wrong. For example,
   in this developer's tmux sessions, the terminal capabilities claim
   that the "cursor up" sequence is ^[M, but the actual sequence
   produced by the "cursor up" key is ^[[A.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
2019-05-13 22:56:27 +02:00
Johannes Schindelin
2efc3ff1cd built-in add -p: respect the interactive.singlekey config setting
The Perl version of `git add -p` supports this config setting to allow
users to input commands via single characters (as opposed to having to
press the <Enter> key afterwards).

This is an opt-in feature because it requires Perl packages
(Term::ReadKey and Term::Cap, where it tries to handle an absence of the
latter package gracefully) to work. Note that at least on Ubuntu, that
Perl package is not installed by default (it needs to be installed via
`sudo apt-get install libterm-readkey-perl`), so this feature is
probably not used a whole lot.

In C, we obviously do not have these packages available, but we just
introduced `read_single_keystroke()` that is similar to what
Term::ReadKey provides, and we use that here.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
2019-05-13 22:56:27 +02:00
Johannes Schindelin
52a7357351 terminal: add a new function to read a single keystroke
Typically, input on the command-line is line-based. It is actually not
really easy to get single characters (or better put: keystrokes).

We provide two implementations here:

- One that handles `/dev/tty` based systems as well as native Windows.
  The former uses the `tcsetattr()` function to put the terminal into
  "raw mode", which allows us to read individual keystrokes, one by one.
  The latter uses `stty.exe` to do the same, falling back to direct
  Win32 Console access.

  Thanks to the refactoring leading up to this commit, this is a single
  function, with the platform-specific details hidden away in
  conditionally-compiled code blocks.

- A fall-back which simply punts and reads back an entire line.

Note that the function writes the keystroke into an `strbuf` rather than
a `char`, in preparation for reading Escape sequences (e.g. when the
user hit an arrow key). This is also required for UTF-8 sequences in
case the keystroke corresponds to a non-ASCII letter.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
2019-05-13 22:56:27 +02:00
Johannes Schindelin
a9cf0d89db terminal: accommodate Git for Windows' default terminal
Git for Windows' Git Bash runs in MinTTY by default, which does not have
a Win32 Console instance, but uses MSYS2 pseudo terminals instead.

This is a problem, as Git for Windows does not want to use the MSYS2
emulation layer for Git itself, and therefore has no direct way to
interact with that pseudo terminal.

As a workaround, use the `stty` utility (which is included in Git for
Windows, and which *is* an MSYS2 program, so it knows how to deal with
the pseudo terminal).

Note: If Git runs in a regular CMD or PowerShell window, there *is* a
regular Win32 Console to work with. This is not a problem for the MSYS2
`stty`: it copes with this scenario just fine.

Also note that we introduce support for more bits than would be
necessary for a mere `disable_echo()` here, in preparation for the
upcoming `enable_non_canonical()` function.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
2019-05-13 22:56:27 +02:00
Johannes Schindelin
2f51f7fe52 terminal: make the code of disable_echo() reusable
We are about to introduce the function `enable_non_canonical()`, which
shares almost the complete code with `disable_echo()`.

Let's prepare for that, by refactoring out that shared code.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
2019-05-13 22:56:27 +02:00
Johannes Schindelin
32b56d5a81 built-in add -p: handle diff.algorithm
The Perl version of `git add -p` reads the config setting
`diff.algorithm` and if set, uses it to generate the diff using the
specified algorithm.

This patch ports that functionality to the C version.

To make sure that this works as intended, we add a regression test case
that tries to specify a bogus diff algorithm and then verifies that `git
diff-files` produced the expected error message.

Note: In that new test case, we actually ignore the exit code of `git
add -p`. The reason is that the C version exits with failure (as one
might expect), but the Perl version does not.

In fact, the Perl version continues happily after the uncolored diff
failed, trying to generate the colored diff, still not catching the
problem, and then it pretends to have succeeded (with exit code 0).

This is arguably a bug in the Perl version, and fixing it is safely
outside the scope of this patch.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
2019-05-13 22:56:27 +02:00
Johannes Schindelin
88d5e66079 built-in add -p: support interactive.diffFilter
The Perl version supports post-processing the colored diff (that is
generated in addition to the uncolored diff, intended to offer a
prettier user experience) by a command configured via that config
setting, and now the built-in version does that, too.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
2019-05-13 22:56:27 +02:00
Johannes Schindelin
f780dae1d3 Merge pull request #2119 from dscho/update-stash-to-current
Update the built-in `git stash` to the latest version
2019-05-13 22:36:56 +02:00
Johannes Schindelin
bd5938339b Merge branch 'dont-spawn-gzip-in-archive'
This topic branch avoids spawning `gzip` when asking `git archive` to
create `.tar.gz` files.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
2019-05-13 22:36:56 +02:00
Johannes Schindelin
82c5157790 Merge pull request #1915 from dscho/open-in-gdb
Add a helper function to start GDB that was already attached to the current process
2019-05-13 22:36:56 +02:00
Johannes Schindelin
61a13cf95e Merge pull request #1900 from tanushree27/remove-ipv6-fallback
[Outreachy] Removed ipv6 fallback
2019-05-13 22:36:56 +02:00
Johannes Schindelin
35fc19990b Merge pull request #1859 from dscho/funny-cased-cwd
Fix t0001 when the current working directory differs in case from the canonical form
2019-05-13 22:36:56 +02:00
Johannes Schindelin
c23a48d531 Merge branch 'mingw-expand-absolute-user-path'
When compiling Git with a runtime prefix (so that it can be installed
into any location, finding its libexec/ directory relative to the
location of the `git` executable), it is convenient to provide
"absolute" Unix-y paths e.g. for http.sslCAInfo, and have those absolute
paths be resolved relative to the runtime prefix.

This patch makes it so for Windows. It is up for discussion whether we
want this for other platforms, too, as long as building with
RUNTIME_PREFIX.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
2019-05-13 22:36:55 +02:00
Johannes Schindelin
a3299e003e Merge branch 'file-url-to-unc-path'
This topic branch teaches Git to accept UNC paths of the form
file://host/share/repository.git.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
2019-05-13 22:36:55 +02:00
Johannes Schindelin
b1b3f57966 Merge branch 'test-unc-fetch'
Fix fetching from UNC paths.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
2019-05-13 22:36:55 +02:00
Johannes Schindelin
6535b4f89a Merge branch 'drive-prefix'
This topic branch allows us to specify absolute paths without the drive
prefix e.g. when cloning.

Example:

	C:\Users\me> git clone https://github.com/git/git \upstream-git

This will clone into a new directory C:\upstream-git, in line with how
Windows interprets absolute paths.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
2019-05-13 22:36:55 +02:00
Johannes Schindelin
c88eede327 Merge pull request #996 from jeffhostetler/jeffhostetler/register_rename_src
diffcore-rename: speed up register_rename_src
2019-05-13 22:36:55 +02:00
Johannes Schindelin
993b49c238 Merge branch 'gitdir-at-unc-root'
This fixes a bug where a .git directory at the root of a network share
(e.g. \\MYSERVER\sharedfolder\.git) was not handled correctly.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
2019-05-13 22:36:55 +02:00
Johannes Schindelin
0fbc98fadd Merge branch 'test-unc-alternates'
The fix we introduced in Git for Windows will be made obsolete by a more
general fix that has been already accepted into upstream Git's `next`
branch.

But we still can introduce a regression test that verifies that this bug
will be caught very quickly, if reintroduced.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
2019-05-13 22:36:54 +02:00
Johannes Schindelin
4fbba5e723 Merge 'aslr' into HEAD
Address Space Layout Randomization (ASLR) allows executables' memory
layout to change at random between runs, and therefore offers a quite
decent protection against many attacks.

We enable ASLR because MSYS2's C compiler offers support for ASLR, and
whatever performance impact it has is neglible, according to
https://insights.sei.cmu.edu/cert/2014/02/differences-between-aslr-on-windows-and-linux.html

This merges the part of https://github.com/git-for-windows/git/pull/612
that does not break Git ;-)

This fixes https://github.com/git-for-windows/git/issues/608

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
2019-05-13 22:36:54 +02:00
Johannes Schindelin
f2175ea5c1 Merge 'fix-externals' into HEAD 2019-05-13 22:36:54 +02:00
Johannes Schindelin
37cf2e633a Merge 'remote-hg-prerequisites' into HEAD
These fixes were necessary for Sverre Rabbelier's remote-hg to work,
but for some magic reason they are not necessary for the current
remote-hg. Makes you wonder how that one gets away with it.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
2019-05-13 22:36:54 +02:00
Johannes Schindelin
1550ae7d2f Merge branch 'cvsexportcommit-crlf'
This used to be "Merge pull request #938 from virtuald/patch-1"

git-cvsexportcommit.perl: Force crlf translation

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
2019-05-13 22:36:54 +02:00
Johannes Schindelin
fec3185956 Merge branch 'reset-stdin'
This topic branch adds the (experimental) --stdin/-z options to `git
reset`. Those patches are still under review in the upstream Git project,
but are already merged in their experimental form into Git for Windows'
`master` branch, in preparation for a MinGit-only release.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
2019-05-13 22:36:54 +02:00
Johannes Schindelin
7bdc9ab8f9 Merge branch 'unhidden-git'
It has been reported that core.hideDotFiles=false stopped working...
This topic branch fixes it.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
2019-05-13 22:36:53 +02:00
Johannes Schindelin
44b2749ecd Merge branch 'add-p-in-c'
Out of all the patch series on the journey to provide `git add
--interactive` and `git add --patch` in a built-in versions, this is the
big one, as can be expected from the fact that the `git add --patch`
functionality makes up over half of the 1,800+ lines of
`git-add--interactive.perl`.

The two patches that stick out are of course the ones to implement hunk
splitting and hunk editing: these operations are fundamentally more
complicated, and less obvious, than the rest of the operations.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
2019-05-13 22:36:46 +02:00
Johannes Schindelin
48e00842ef Merge branch 'add-i-fixes'
While re-implementing `git add -i` and `git add -p` in C, I tried to
make sure that there is test coverage for all of the features I convert
from Perl to C, to give me some confidence in the correctness from
running the test suite both with `GIT_TEST_ADD_I_USE_BUILTIN=true` and
with `GIT_TEST_ADD_I_USE_BUILTIN=false`.

However, I discovered that there are a couple of gaps. This patch series
intends to close them.

The first patch might actually not be considered a gap by some: it
basically removes the need for the `TTY` prerequisite in the `git add
-i` tests to verify that the output is colored all right. This change is
rather crucial for me, though: on Windows, where the conversion to a
built-in shows the most obvious benefits, there are no pseudo terminals
(yet), therefore `git.exe` cannot work with them (even if the MSYS2 Perl
interpreter used by Git for Windows knows about some sort of pty
emulation). And I *really* wanted to make sure that the colors work on
Windows, as I personally get a lot out of those color cues.

The patch series ends by addressing two issues that are not exactly
covering testing gaps:

- While adding a test case, I noticed that `git add -p` exited with
  *success* when it could not even generate a diff. This is so obviously
  wrong that I had to fix it right away (I noticed, actually, because my
  in-progress built-in `git add -p` failed, and the Perl version did
  not), and I used the same test case to verify that this is fixed once
  and for all.

- While working on covering those test gaps, I noticed a problem in an
  early version of the built-in version of `git add -p` where the `git
  apply --allow-overlap` mode failed to work properly, for little
  reason, and I fixed it real quick.

  It would seem that the `--allow-overlap` function is not only
  purposefully under-documented, but also purposefully under-tested,
  probably to discourage its use. I do not quite understand what I
  perceive to be Junio's aversion to that option, but I did not feel
  like I should put up a battle here, so I did not accompany this fix
  with a new test script.

  In the end, the built-in version of `git add -p` does not use the
  `--allow-overlap` function at all, anyway. Which should make everybody
  a lot happier.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
2019-05-13 22:36:45 +02:00
Johannes Schindelin
48eef77cf0 Merge branch 'add-i-in-c-all-except-patch'
This patch series implements the rest of the commands in `git add -i`'s
main loop: `update`, `revert`, `add_untracked`, `patch`, `diff`, and
`quit`. Apart from `quit`, these commands are all very similar in that
they first build a list of files, display it, let the user choose which
ones to act on, and then perform the action.

Note that the `patch` command is not actually converted to C, not
completely at least: the built-in version simply hands off to `git
add--interactive` after letting the user select which files to act on.

The reason for this omission is practicality. Out of the 1,800+ lines of
`git-add--interactive.perl`, over a thousand deal *just* with the `git
add -p` part. I did convert that functionality already (to be
contributed in a separate patch series), discovering that there is so
little overlap between the `git add --patch` part and the rest of `git
add --interactive` that I could put the former into a totally different
file: `add-patch.c`. Just a teaser ;-)

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
2019-05-13 22:36:45 +02:00
Johannes Schindelin
801b4b7c4c Merge branch 'add-i-in-c-status-and-help'
The first part of the long journey to a fully built-in `git add -i`.

It reflects the part that was submitted a couple of times (see
https://github.com/gitgitgadget/git/pull/103) during the Outreachy
project by Slavica Đukić that continued the journey based on an initial
patch series by Daniel Ferreira.

This part only implements the `status` and the `help` part, like
Slavica's last iteration did, in the interest of making the review
remotely more reviewable. I fear that this attempt of making it a bit
more reviewable is pretty futile, as so many things changed. So I will
ask the reviewers for forgiveness: please be kind, and give this sort of
a fresh review.

I threw in a couple of major changes on top of that iteration, though:

- The original plan was to add a helper (`git add--helper`) that takes
  over more and more responsibility from the Perl script over the course
  of the conversion.

  This plan is no longer in effect, as I encountered a serious problem
  with that: the MSYS2 runtime used by the Perl interpreter which Git
  for Windows employs to run `git add -i` has a curious bug (that is
  safely outside the purview of this here patch series) where it fails
  to read from standard input after it spawned a non-MSYS2 program that
  reads from standard input. To keep my `git add -i` in a working state,
  I therefore adopted a different strategy:

  Just like `git difftool` was converted by starting with a built-in
  that did nothing but handing off to the scripted version, guarded by
  the (opt-in) `difftool.useBuiltin` config setting, I start this patch
  series by a built-in `add -i` that does nothing else but state that it
  is not implemented yet, guarded by the (opt-in)
  `add.interactive.useBuiltin` config setting.

  In contrast to the `git difftool` situation, it is quite a bit easier
  here, as we do not even have to rename the script to
  `git-legacy-add--interactive.perl`: the `add--interactive` command is
  an implementation detail that users are not even supposed to know
  about. Therefore, we can implement that road fork between the built-in
  and the scripted version in `builtin/add.c`, i.e. in the user-facing
  `git add` command.

  This will also naturally help with the transition to a fully built-in
  `git add -i`/`git add -p`, as we saw with the built-in `git rebase`
  how important it is for end users to have an escape hatch (and for
  that reason, tried our best to provide the same with the built-in `git
  stash`).

- The `help` command was actually not hooked up in `git add -i`, but was
  only available as a special option of the `git add--helper` command.
  As that command no longer exists, I kind of *had* to implement
  some way to let the built-in `git add -i` show the help text.

- The main loop of `git add -i` (i.e. the thing that lets you choose
  `status` or `help`) is now implemented (but only lists `status` and
  `help`, of course), as it makes use of that feature that took the main
  chunk of the Outreachy project: the function to determine unique
  prefixes of a list of strings.

- Speaking of the unique prefixes: the functionality to determine those
  is now encapsulated in the `prefix-map.c` file, and I also added a
  regression test.

- Speaking of the tests: I also implemented support for the environment
  variable `GIT_TEST_ADD_I_USE_BUILTIN`: by setting it, the test suite
  can be forced to use the built-in, or the Perl script, version of `git
  add -i`. Needless to say: by the end of this patch series, running the
  test suite with `GIT_TEST_ADD_I_USE_BUILTIN=true` will still result in
  a ton of test failures due to not-yet-implemented commands, but it
  will also demonstrate what *already* works.

- Since the main loop starts not only by showing the status, but
  refreshes the index before that, I added that, and I actually
  refactored that code into a new function
  (`repo_refresh_and_write_index()`), as it will be used a couple of
  times by the end of the complete conversion of `git add -i` into a
  built-in command.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
2019-05-13 22:36:45 +02:00
Johannes Schindelin
755ff1e3bd commit --interactive: make it work with the built-in add -i
The built-in `git add -i` machinery obviously has its `the_repository`
structure initialized at the point where `cmd_commit()` calls it, and
therefore does not look at the environment variable `GIT_INDEX_FILE`.

But it has to, because the index was already locked, and we want to ask
the interactive add machinery to work on the `index.lock` file instead
of the `index` file.

Technically, we could teach `run_add_i()` (and `run_add_p()`) to look
specifically at that environment variable, but the entire idea of
passing in a parameter of type `struct repository *` is to allow working
on multiple repositories (and their index files) independently.

So let's instead override the `index_file` field of that structure
temporarily.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
2019-05-13 22:36:44 +02:00
Johannes Schindelin
0eb89f8e8a built-in add -p: show helpful hint when nothing can be staged
This patch will make `git add -p` show "No changes." or "Only binary
files changed." in that case.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
2019-05-13 22:36:44 +02:00
Johannes Schindelin
99edd47137 built-in add -p: implement the "checkout" patch modes
This patch teaches the built-in `git add -p` machinery all the tricks it
needs to know in order to act as the work horse for `git checkout -p`.

Apart from the minor changes (slightly reworded messages, different
`diff` and `apply --check` invocations), it requires a new function to
actually apply the changes, as `git checkout -p` is a bit special in
that respect: when the desired changes do not apply to the index, but
apply to the work tree, Git does not fail straight away, but asks the
user whether to apply the changes to the worktree at least.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
2019-05-13 22:36:44 +02:00
Johannes Schindelin
3d0f2f1b1b built-in add -p: only show the applicable parts of the help text
When displaying the only hunk in a file's diff, the prompt already
excludes the commands to navigate to the previous/next hunk.

Let's also let the `?` command show only the help lines corresponding to
the commands that are displayed in the prompt.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
2019-05-13 22:36:44 +02:00
Johannes Schindelin
ad76b63779 built-in add -p: implement the "stash" and "reset" patch modes
The `git stash` and `git reset` commands support a `--patch` option, and
both simply hand off to `git add -p` to perform that work. Let's teach
the built-in version of `git add -p` do perform that work, too.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
2019-05-13 22:36:44 +02:00
Johannes Schindelin
a5de453e3d built-in add -p: implement the 'q' ("quit") command
This command is actually very similar to the 'd' ("do not stage this
hunk or any of the later hunks in the file") command: it just does
something on top, namely leave the loop and return a value indicating
that we're quittin'.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
2019-05-13 22:36:44 +02:00
Johannes Schindelin
1c76069775 stash -p: respect the add.interactive.usebuiltin setting
As `git add` traditionally did not expose the `--patch=<mode>` modes via
command-line options, `git stash` had to call `git add--interactive`
directly.

But this prevents the built-in `add -p` from kicking in, as
`add--interactive` is the Perl script.

So let's introduce support for an optional `<mode>` argument in `git add
--patch[=<mode>]`, and use that in `git stash -p`, so that the built-in
interactive add can do its job if configured.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
2019-05-13 22:36:44 +02:00
Johannes Schindelin
e838305ec4 built-in add -p: implement the '/' ("search regex") command
This patch implements the hunk searching feature in the C version of
`git add -p`.

A test is added to verify that this behavior matches the one of the Perl
version of `git add -p`.

Note that this involves a change of behavior: the Perl version uses (of
course) the Perl flavor of regular expressions, while this patch uses
the regcomp()/regexec(), i.e. POSIX extended regular expressions. In
practice, this behavior change is unlikely to matter.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
2019-05-13 22:36:44 +02:00
Johannes Schindelin
8f72631cdc built-in add -p: prepare for patch modes other than "stage"
The Perl script backing `git add -p` is used not only for that command,
but also for `git stash -p`, `git reset -p` and `git checkout -p`.

In preparation for teaching the C version of `git add -p` to support
also the latter commands, let's abstract away what is "stage" specific
into a dedicated data structure describing the differences between the
patch modes.

As we prepare for calling the built-in `git add -p` in
`run_add_interactive()` via code paths that have not let `add_config()`
do its work, we have to make sure to re-parse the config using that
function in those cases.

Finally, please note that the Perl version tries to make sure that the
diffs are only generated for the modified files. This is not actually
necessary, as the calls to Git's diff machinery already perform that
work, and perform it well. This makes it unnecessary to port the
`FILTER` field of the `%patch_modes` struct, as well as the
`get_diff_reference()` function.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
2019-05-13 22:36:44 +02:00
Johannes Schindelin
801cd5209b apply --allow-overlap: fix a corner case
Yes, yes, this is supposed to be only a band-aid option for `git add -p`
not Doing The Right Thing. But as long as we carry the `--allow-overlap`
option, we might just as well get it right.

This fixes the case where one hunk inserts a line before the first one,
and a hunk whose context overlaps with the first one's appends a line at
the end.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
2019-05-13 22:36:43 +02:00
Johannes Schindelin
559e51b8c7 built-in add -p: implement the 'g' ("goto") command
With this patch, it is now possible to see a summary of the available
hunks and to navigate between them (by number).

A test is added to verify that this behavior matches the one of the Perl
version of `git add -p`.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
2019-05-13 22:36:43 +02:00
Johannes Schindelin
251f323598 git add -p: use non-zero exit code when the diff generation failed
The first thing `git add -p` does is to generate a diff. If this diff
cannot be generated, `git add -p` should not continue as if nothing
happened, but instead fail.

What we *actually* do here is much broader: we now verify for *every*
`run_cmd_pipe()` call that the spawned process actually succeeded.

Note that we have to change two callers in this patch, as we need to
store the spawned process' output in a local variable, which means that
the callers can no longer decide whether to interpret the `return <$fh>`
in array or in scalar context.

This bug was noticed while writing a test case for the diff.algorithm
feature, and we let that test case double as a regression test for this
fixed bug, too.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
2019-05-13 22:36:43 +02:00