Re: [PATCH v6 0/9] git add -i: add a rudimentary version in C (supporting only status and help so far)

> This is the first leg on the long journey to a fully built-in git add -i
> (next up: parts 2 [https://github.com/gitgitgadget/git/pull/171], 3
> [https://github.com/gitgitgadget/git/pull/172], 4
> [https://github.com/gitgitgadget/git/pull/173], 5
> [https://github.com/gitgitgadget/git/pull/174], and 6
> [https://github.com/gitgitgadget/git/pull/175]). Note: the latter PRs are
> not necessarily up to date, and will be re-targeted to the appropriate
> branches in https://github.com/gitster/git as soon as Junio picks them up.
>
> This here patch series reflects the part that was submitted a couple of
> times (see https://github.com/gitgitgadget/git/pull/103) during the
> Outreachy project by Slavica Ðukic that continued the journey based on an
> initial patch series by Daniel Ferreira.
>
> It only implements the status and the help part, in the interest of making
> the review remotely more reviewable.
>
> As I am a heavy user of git add -p myself and use a patched version for
> several months already (it is so nice to not suffer over one second startup
> until the MSYS2 Perl finally shows me anything, instead it feels
> instantaneous), I integrated these patch series into Git for Windows
> already, as an opt-in feature guarded by the config variable
> add.interactive.useBuiltin (and Git for Windows' installer knows to detect
> this version and offer the option in the graphical user interface).

> Changes since v4:
>
>  * Rebased onto current master to make use of Thomas Gummerer's
>    repo_refresh_and_write_index() as well as to avoid merge conflicts with
>    Eric Wong's work on struct hashmap.
>  * Instead of rolling a dedicated data struct to simulate a Trie, we now use
>    string-list extensively (an unsorted copy and a sorted one, the latter to
>    determine unique prefixes). This had massive ramifications on the rest of
>    the patches... For example, the struct command_item structure no longer
>    contains the name field, but is intended to be a util in a string_list.
>  * Changed the commit messages and author lines to reflect Slavica's name
>    correctly.
>  * Touched up a couple commit messages.
>
> Changes since v3:
>
>  * Rebased to v2.23.0 to reduce friction.
>  * free_diffstat_info() is now made public as well, and used, to avoid a
>    memory leak.
>  * Prepared the patches for ew/hashmap (which is strict about the hashmap
>    entries' type in hashmap_entry_init() and friends).
>  * The private data types have been moved from prefix-map.h to prefix-map.c.
>  * A lot of int types were converted to more appropriate size_t in
>    prefix-map.c.
>  * A misleading parameter name list was renamed to the correct array.
>  * The code comment above find_unique_prefixes() was (hopefully) improved.
>  * The run_help() function's signature now reflects that most of the
>    parameters are actually unused.
>
> Changes since v2:
>
>  * Rebased to master to avoid merge conflicts.
>  * Renumbered the prefix-map test to avoid conflicts with two patch series
>    that are currently in-flight in pu.
>
> Changes since v1:
>
>  * The config machinery was reworked completely, to not use a callback to
>    git_config(), but instead to query the config via the repo_config_get_*()
>    functions. This also prevents a future "Huh???" moment: the internal add
>    --interactive API accepts a parameter of type struct repository *r, but
>    the previous configuration did not use that to query the config (and
>    could in the future be a repository other than the_repository).
>
>
>  * As a consequence, the color sequences are no longer stored in file-local
>    variables, but passed around via a struct.
>
>
>  * Instead of using the magical constant -2 to quit the main loop, it is now
>    defined as LIST_AND_CHOOSE_QUIT (and likewise, LIST_AND_CHOOSE_ERROR is
>    defined as -1 and used where appropriate).
>
>
>  * Improved the add_prefix_item() function by avoiding buffer overruns, not
>    reusing the struct that is used for lookup also for adding the new item,
>    and by strengthening the bug check.
>
> Daniel Ferreira (2):
>   diff: export diffstat interface
>   built-in add -i: implement the `status` command
>
> Johannes Schindelin (4):
>   Start to implement a built-in version of `git add --interactive`
>   built-in add -i: implement the main loop
>   built-in add -i: show unique prefixes of the commands
>   built-in add -i: support `?` (prompt help)
>
> Slavica Đukić (3):
>   built-in add -i: color the header in the `status` command
>   built-in add -i: use color in the main loop
>   built-in add -i: implement the `help` command
>
>  Documentation/config/add.txt |   5 +
>  Makefile                     |   1 +
>  add-interactive.c            | 651 +++++++++++++++++++++++++++++++++++
>  add-interactive.h            |   8 +
>  builtin/add.c                |  12 +
>  diff.c                       |  39 +--
>  diff.h                       |  20 ++
>  t/README                     |   4 +
>  t/t3701-add-interactive.sh   |  25 ++
>  9 files changed, 742 insertions(+), 23 deletions(-)
>  create mode 100644 add-interactive.c
>  create mode 100644 add-interactive.h
>
>
> base-commit: 566a1439f6f56c2171b8853ddbca0ad3f5098770
> Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-170%2Fdscho%2Fadd-i-in-c-status-and-help-v6
> Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-170/dscho/add-i-in-c-status-and-help-v6
> Pull-Request: https://github.com/gitgitgadget/git/pull/170
>
> Range-diff vs v5:
>
>   1:  ff59d2d0b3 !  1:  5d9962d434 Start to implement a built-in version of `git add --interactive`
>      @@ -2,31 +2,31 @@
>
>           Start to implement a built-in version of `git add --interactive`
>
>      -    This is hardly the first conversion of a Git command that is implemented
>      -    as a script to a built-in. So far, the most successful strategy for such
>      -    conversions has been to add a built-in helper and call that for more and
>      -    more functionality from the script, as more and more parts are
>      -    converted.
>      +    Unlike previous conversions to C, where we started with a built-in
>      +    helper, we start this conversion by adding an interception in the
>      +    `run_add_interactive()` function when the new opt-in
>      +    `add.interactive.useBuiltin` config knob is turned on (or the
>      +    corresponding environment variable `GIT_TEST_ADD_I_USE_BUILTIN`), and
>      +    calling the new internal API function `run_add_i()` that is implemented
>      +    directly in libgit.a.
>
>      -    With the interactive add, we choose a different strategy. The sole
>      -    reason for this is that on Windows (where such a conversion has the most
>      -    benefits in terms of speed and robustness) we face the very specific
>      -    problem that a `system()` call in Perl seems to close `stdin` in the
>      -    parent process when the spawned process consumes even one character from
>      -    `stdin`. And that just does not work for us here, as it would stop the
>      -    main loop as soon as any interactive command was performed by the
>      -    helper. Which is almost all of the commands in `git add -i`.
>      -
>      -    It is almost as if Perl told us once again that it does not want us to
>      -    use it on Windows.
>      +    At this point, the built-in version of `git add -i` only states that it
>      +    cannot do anything yet. In subsequent patches/patch series, the
>      +    `run_add_i()` function will gain more and more functionality, until it
>      +    is feature complete. The whole arc of the conversion can be found in the
>      +    PRs #170-175 at https://github.com/gitgitgadget/git.
>
>      -    Instead, we follow the opposite route where we start with a bare-bones
>      -    version of the built-in interactive add, guarded by the new
>      -    `add.interactive.useBuiltin` config variable, and then add more and more
>      -    functionality to it, until it is feature complete.
>      +    The "--helper approach" can unfortunately not be used here: on Windows
>      +    we face the very specific problem that a `system()` call in
>      +    Perl seems to close `stdin` in the parent process when the spawned
>      +    process consumes even one character from `stdin`. Which prevents us from
>      +    implementing the main loop in C and still trying to hand off to the Perl
>      +    script.
>
>      -    At this point, the built-in version of `git add -i` only states that it
>      -    cannot do anything yet ;-)
>      +    The very real downside of the approach we have to take here is that the
>      +    test suite won't pass with `GIT_TEST_ADD_I_USE_BUILTIN=true` until the
>      +    conversion is complete (the `--helper` approach would have let it pass,
>      +    even at each of the incremental conversion steps).
>
>           Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
>
>      @@ -99,12 +99,14 @@
>        	struct argv_array argv = ARGV_ARRAY_INIT;
>       +	int use_builtin_add_i =
>       +		git_env_bool("GIT_TEST_ADD_I_USE_BUILTIN", -1);
>      -+	if (use_builtin_add_i < 0)
>      -+		git_config_get_bool("add.interactive.usebuiltin",
>      -+				    &use_builtin_add_i);
>       +
>      -+	if (use_builtin_add_i == 1 && !patch_mode)
>      -+		return !!run_add_i(the_repository, pathspec);
>      ++	if (!patch_mode) {
>      ++		if (use_builtin_add_i < 0)
>      ++			git_config_get_bool("add.interactive.usebuiltin",
>      ++					    &use_builtin_add_i);
>      ++		if (use_builtin_add_i == 1)
>      ++			return !!run_add_i(the_repository, pathspec);
>      ++	}
>
>        	argv_array_push(&argv, "add--interactive");
>        	if (patch_mode)
>   2:  2fc8cc3546 =  2:  f42d7b1310 diff: export diffstat interface
>   3:  6aaa0de4f4 =  3:  4836191271 built-in add -i: implement the `status` command
>   4:  e405f07110 =  4:  d61cf9daeb built-in add -i: color the header in the `status` command
>   5:  25590fbbbe !  5:  b0c04e6ec6 built-in add -i: implement the main loop
>      @@ -7,33 +7,34 @@
>           function that we conveniently introduced for use by the `status`
>           command.
>
>      -    Apart from the "and choose" part, there are more differences between the
>      -    way the `status` command calls the `list_and_choose()` function in the
>      -    Perl version of `git add -i` compared to the other callers of said
>      -    function. The most important ones:
>      +    In contrast to the Perl version, in the built-in interactive `add`, we
>      +    will keep the `list()` function (which only displays items) and the
>      +    `list_and_choose()` function (which uses `list()` to display the items,
>      +    and only takes care of the "and choose" part) separate.
>
>      -    - The list is not only shown, but the user is also asked to make a
>      -      choice, possibly selecting multiple entries.
>      +    The `list_and_choose()` function, as implemented in
>      +    `git-add--interactive.perl` knows a few more tricks than the function we
>      +    introduce in this patch:
>
>      -    - The list of items is prefixed with a marker indicating what items have
>      -      been selected, if multi-selection is allowed.
>      +    - There is a flag to let the user select multiple items.
>
>      -    - Initially, for each item a unique prefix (if there exists any within
>      -      the given parameters) is determined, and shown in the list, and
>      +    - In multi-select mode, the list of items is prefixed with a marker
>      +      indicating what items have been selected.
>      +
>      +    - Initially, for each item a unique prefix is determined (if there
>      +      exists any within the given parameters), and shown in the list, and
>             accepted as a shortcut for the selection.
>
>      -    These features will be implemented later, except the part where the user
>      -    can choose a command. At this stage, though, the built-in `git add -i`
>      -    still only supports the `status` command, with the remaining commands to
>      -    follow over the course of the next commits.
>      +    These features will be implemented in the C version later.
>
>      -    In addition, we also modify `list()` to support displaying the commands
>      -    in columns, even if there is currently only one.
>      +    This patch does not add any new main loop command, of course, the
>      +    built-in `git add -i` still only supports the `status` command. The
>      +    remaining commands to follow over the course of the next commits.
>
>      -    The Perl script `git-add--interactive.perl` mixed the purposes of the
>      -    "list" and the "and choose" part into the same function. In the C
>      -    version, we will keep them separate instead, calling the `list()`
>      -    function from the `list_and_choose()` function.
>      +    To accommodate for listing the commands in columns, preparing for the
>      +    commands that will be implemented over the course of the next
>      +    patches/patch series, we teach the `list()` function to do precisely
>      +    that.
>
>           Note that we only have a prompt ending in a single ">" at this stage;
>           later commits will add commands that display a double ">>" to indicate
>      @@ -101,7 +102,7 @@
>       +	ssize_t res = LIST_AND_CHOOSE_ERROR;
>       +
>       +	for (;;) {
>      -+		char *p, *endp;
>      ++		char *p;
>       +
>       +		strbuf_reset(&input);
>       +
>      @@ -133,6 +134,7 @@
>       +			}
>       +
>       +			if (isdigit(*p)) {
>      ++				char *endp;
>       +				index = strtoul(p, &endp, 10) - 1;
>       +				if (endp != p + sep)
>       +					index = -1;
>   6:  57fdc01463 !  6:  b6459be5eb built-in add -i: show unique prefixes of the commands
>      @@ -177,7 +177,7 @@
>       +	find_unique_prefixes(items);
>       +
>        	for (;;) {
>      - 		char *p, *endp;
>      + 		char *p;
>
>        		strbuf_reset(&input);
>
>   7:  77ad5f333a =  7:  bdf9058d9e built-in add -i: support `?` (prompt help)
>   8:  3d0b172a7f =  8:  eafeedc49b built-in add -i: use color in the main loop
>   9:  85e508ef11 =  9:  7fda76255a built-in add -i: implement the `help` command
>
> --
> gitgitgadget
>