Re: [GSoC Patch v5 1/4] path: introduce append_formatted_path() for shared path formatting

> The path-formatting logic in builtin/rev-parse.c is tightly coupled
> to that command and writes directly to stdout, making it impossible
> for other builtins to reuse.
> 
> Extract the core algorithm into append_formatted_path() in path.c
> and expose a path_format enum in path.h so that any builtin can
> format paths consistently without duplicating logic.

> Mentored-by: Justin Tobler <jltobler@gmail.com>
> Mentored-by: Lucas Seiki Oshiro <lucasseikioshiro@gmail.com>
> Signed-off-by: K Jayatheerth <jayatheerthkulkarni2005@gmail.com>
> ---
>   path.c | 70 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
>   path.h | 36 ++++++++++++++++++++++++++++++
>   2 files changed, 106 insertions(+)
> 
> diff --git a/path.c b/path.c
> index d7e17bf174..5e83e3e4f6 100644
> --- a/path.c
> +++ b/path.c
> @@ -1579,6 +1579,76 @@ char *xdg_cache_home(const char *filename)
>   	return NULL;
>   }
>   
> +void append_formatted_path(struct strbuf *dest, const char *path,
> +			   const char *prefix, enum path_format format)
> +{
> +	switch (format) {
> +	case PATH_FORMAT_DEFAULT:
> +	case PATH_FORMAT_UNMODIFIED:
> +		strbuf_addstr(dest, path);
> +		break;
> +
> +	case PATH_FORMAT_RELATIVE: {
> +		struct strbuf relative_buf = STRBUF_INIT;
> +		struct strbuf real_path = STRBUF_INIT;
> +		struct strbuf real_prefix = STRBUF_INIT;
> +		char *cwd = NULL;
> +
> +		/*
> +		 * We don't ever produce a relative path if prefix is NULL,
> +		 * so set the prefix to the current directory so that we can
> +		 * produce a relative path whenever possible.
> +		 */
> +		if (!prefix)
> +			prefix = cwd = xgetcwd();
> +
> +		if (!is_absolute_path(path)) {
> +			strbuf_realpath_forgiving(&real_path, path, 1);
> +			path = real_path.buf;
> +		}
> +		if (!is_absolute_path(prefix)) {
> +			strbuf_realpath_forgiving(&real_prefix, prefix, 1);
> +			prefix = real_prefix.buf;
> +		}
> +
> +		strbuf_addstr(dest, relative_path(path, prefix, &relative_buf));
> +
> +		strbuf_release(&relative_buf);
> +		strbuf_release(&real_path);
> +		strbuf_release(&real_prefix);
> +		free(cwd);
> +		break;
> +	}
> +
> +	case PATH_FORMAT_RELATIVE_IF_SHARED: {
> +		struct strbuf relative_buf = STRBUF_INIT;
> +
> +		/*
> +		 * If we're using RELATIVE_IF_SHARED mode, then we want an
> +		 * absolute path unless the two share a common prefix, so don't
> +		 * default the prefix to the current working directory. Doing so
> +		 * would cause a relative path to always be produced if possible.
> +		 */
> +		strbuf_addstr(dest, relative_path(path, prefix, &relative_buf));
> +		strbuf_release(&relative_buf);
> +		break;
> +	}
> +
> +	case PATH_FORMAT_CANONICAL: {
> +		struct strbuf canonical_buf = STRBUF_INIT;
> +
> +		strbuf_realpath_forgiving(&canonical_buf, path, 1);
> +		strbuf_addbuf(dest, &canonical_buf);
> +
> +		strbuf_release(&canonical_buf);
> +		break;
> +	}
> +
> +	default:
> +		BUG("unknown path_format value %d", format);
> +	}
> +}
> +
>   REPO_GIT_PATH_FUNC(squash_msg, "SQUASH_MSG")
>   REPO_GIT_PATH_FUNC(merge_msg, "MERGE_MSG")
>   REPO_GIT_PATH_FUNC(merge_rr, "MERGE_RR")
> diff --git a/path.h b/path.h
> index 0434ba5e07..6aca53b100 100644
> --- a/path.h
> +++ b/path.h
> @@ -262,6 +262,42 @@ enum scld_error safe_create_leading_directories_no_share(char *path);
>   int safe_create_file_with_leading_directories(struct repository *repo,
>   					      const char *path);
>   
> +/**
> + * The formatting strategy to apply when writing a path into a buffer.
> + */
> +enum path_format {
> +	/*
> +	 * Represents the default formatting behavior. Treated as
> +	 * PATH_FORMAT_UNMODIFIED by append_formatted_path().
> +	 */
> +	PATH_FORMAT_DEFAULT,
> +
> +	/* Output the path exactly as-is without any modifications. */
> +	PATH_FORMAT_UNMODIFIED,
> +
> +	/* Output a path relative to the provided directory prefix. */
> +	PATH_FORMAT_RELATIVE,
> +
> +	/* Output a relative path only if the path shares a root with the prefix. */
> +	PATH_FORMAT_RELATIVE_IF_SHARED,
> +
> +	/* Output a fully resolved, absolute canonical path. */
> +	PATH_FORMAT_CANONICAL
> +};
> +
> +/**
> + * Format a path according to the specified formatting strategy and append
> + * the result to the given strbuf.
> + *
> + * `dest`   : The string buffer to append the formatted path to.
> + * `path`   : The path string that needs to be formatted.
> + * `prefix` : The directory prefix to calculate relative offsets against.
> + * Pass NULL to default to the current working directory where applicable.
> + * `format` : The formatting behavior rule to execute.
> + */
> +void append_formatted_path(struct strbuf *dest, const char *path,
> +			   const char *prefix, enum path_format format);
> +
>   # ifdef USE_THE_REPOSITORY_VARIABLE
>   #  include "strbuf.h"
>   #  include "repository.h"