test: add test cases for relative_path

Add subcommand "relative_path" in test-path-utils, and add test cases
in t0060.

Johannes tested this commit on Windows, and found that some relative_path
tests should be skipped on Windows. This is because the bash on Windows
rewrites arguments of regular Windows programs, such as git and the
test helpers, if the arguments look like absolute POSIX paths. As a
consequence, the actual tests performed are not what the tests scripts
expect.

The tests that need *not* be skipped are those where the two paths passed
to 'test-path-utils relative_path' have the same prefix and the result is
expected to be a relative path. This is because the rewriting changes
"/a/b" to "D:/Src/MSysGit/a/b", and when both inputs are extended the same
way, this just cancels out in the relative path computation.

Signed-off-by: Jiang Xin <worldhello.net@gmail.com>
Signed-off-by: Johannes Sixt <j6t@kdbg.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
path.c: refactor relative_path(), not only strip prefix

Original design of relative_path() is simple, just strip the prefix
(*base) from the absolute path (*abs). In most cases, we need a real
relative path, such as: ../foo, ../../bar. That's why there is another
reimplementation (path_relative()) in quote.c.

Borrowed some codes from path_relative() in quote.c to refactor
relative_path() in path.c, so that it could return real relative path,
and user can reuse this function without reimplement his/her own.
The function path_relative() in quote.c will be substituted, and I
would use the new relative_path() function when implement the
interactive git-clean later.

Different results for relative_path() before and after this refactor:

    abs path  base path  relative (original)  relative (refactor)
    ========  =========  ===================  ===================
    /a/b/c/   /a/b       c/                   c/
    /a/b//c/  //a///b/   c/                   c/
    /a/b      /a/b       .                    ./
    /a/b/     /a/b       .                    ./
    /a        /a/b/      /a                   ../
    /         /a/b/      /                    ../../
    /a/c      /a/b/      /a/c                 ../c
    /x/y      /a/b/      /x/y                 ../../x/y
    /a/b      (empty)    /a/b                 /a/b
    /a/b      (null)     /a/b                 /a/b

    a/b/c/    a/b/       c/                   c/
    a/b/c/    a/b        c/                   c/
    a/b//c    a//b       c                    c
    a/b/      a/b/       .                    ./
    a/b/      a/b        .                    ./
    a         a/b        a                    ../
    x/y       a/b/       x/y                  ../../x/y
    a/c       a/b        a/c                  ../c
    a/b       (empty)    a/b                  a/b
    a/b       (null)     a/b                  a/b

    (empty)   (null)     (empty)              ./
    (empty)   (empty)    (empty)              ./
    (empty)   /a/b       (empty)              ./
    (null)    (null)     (null)               ./
    (null)    (empty)    (null)               ./
    (null)    /a/b       (segfault)           ./

You may notice that return value "." has been changed to "./".
It is because:

 * Function quote_path_relative() in quote.c will show the relative
   path as "./" if abs(in) and base(prefix) are the same.

 * Function relative_path() is called only once (in setup.c), and
   it will be OK for the return value as "./" instead of ".".

Signed-off-by: Jiang Xin <worldhello.net@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
quote.c: substitute path_relative with relative_path

Substitute the function path_relative in quote.c with the function
relative_path. Function relative_path can be treated as an enhanced
and robust version of path_relative.

Outputs of path_relative and it's replacement (relative_path) are the
same for the following cases:

    path      prefix     output of path_relative  output of relative_path
    ========  =========  =======================  =======================
    /a/b/c/   /a/b/      c/                       c/
    /a/b/c    /a/b/      c                        c
    /a/       /a/b/      ../                      ../
    /         /a/b/      ../../                   ../../
    /a/c      /a/b/      ../c                     ../c
    /x/y      /a/b/      ../../x/y                ../../x/y
    a/b/c/    a/b/       c/                       c/
    a/        a/b/       ../                      ../
    x/y       a/b/      ../../x/y                 ../../x/y
    /a/b      (empty)    /a/b                     /a/b
    /a/b      (null)     /a/b                     /a/b
    a/b       (empty)    a/b                      a/b
    a/b       (null)     a/b                      a/b

But if both of the path and the prefix are the same, or the returned
relative path should be the current directory, the outputs of both
functions are different. Function relative_path returns "./", while
function path_relative returns empty string.

    path      prefix     output of path_relative  output of relative_path
    ========  =========  =======================  =======================
    /a/b/     /a/b/      (empty)                  ./
    a/b/      a/b/       (empty)                  ./
    (empty)   (null)     (empty)                  ./
    (empty)   (empty)    (empty)                  ./

But not panic, the callers of path_relative can handle such cases, or
never encounter this issue at all. E.g.

 * In function quote_path_relative, if the output of path_relative is
   empty, append "./" to it, like:

       if (!out->len)
           strbuf_addstr(out, "./");

 * Another caller is write_name_quoted_relative, which is only used by
   builtin/ls-files.c. git-ls-files only show files, so path of files
   will never be identical with the prefix of a directory.

The following differences show that path_relative can not handle
extra slashes properly.

    path      prefix     output of path_relative  output of relative_path
    ========  =========  =======================  =======================
    /a//b//c/ //a/b//    ../../../../a//b//c/     c/
    a/b//c    a//b       ../b//c                  c

And if prefix has no trailing slash, path_relative can not work properly
either. But since prefix always has a trailing slash, so it's not a
problem.

    path      prefix     output of path_relative  output of relative_path
    ========  =========  =======================  =======================
    /a/b/c/   /a/b       b/c/                     c/
    /a/b      /a/b       b                        ./
    /a/b/     /a/b       b/                       ./
    /a        /a/b/      ../../a                  ../
    a/b/c/    a/b        b/c/                     c/
    a/b/      a/b        b/                       ./
    a         a/b        ../a                     ../
    x/y       a/b/       ../x/y                   ../../x/y
    a/c       a/b        c                        ../c
    /a/       /a/b       (empty)                  ../
    (empty)   /a/b       ../../                   ./

Signed-off-by: Jiang Xin <worldhello.net@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Signed-off-by: Jiang Xin <worldhello.net@gmail.com>
Refactor quote_path_relative, remove unused params

After substitute path_relative() in quote.c with relative_path() from
path.c, parameters (such as len and prefix_len) are obsolete in function
quote_path_relative(). Remove unused parameters and change the order of
parameters for quote_path_relative() function.

Signed-off-by: Jiang Xin <worldhello.net@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Refactor write_name_quoted_relative, remove unused params

After substitute path_relative() in quote.c with relative_path() from
path.c, parameters (such as len and prefix_len) are obsolete in function
write_name_quoted_relative(). Remove unused parameters from
write_name_quoted_relative() and related functions.

Signed-off-by: Jiang Xin <worldhello.net@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
git-clean: refactor git-clean into two phases

Before introducing interactive git-clean, refactor git-clean operations
into two phases:

 * hold cleaning items in del_list,
 * and remove them in a separate loop at the end.

We will introduce interactive git-clean between the two phases. The
interactive git-clean will show what would be done and must confirm
before do real cleaning.

Signed-off-by: Jiang Xin <worldhello.net@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
git-clean: add support for -i/--interactive

Show what would be done and the user must confirm before actually
cleaning.

    Would remove ...
    Would remove ...
    Would remove ...

    Remove [y/n]?

Press "y" to start cleaning, and press "n" if you want to abort.

Signed-off-by: Jiang Xin <worldhello.net@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
git-clean: show items of del_list in columns

When there are lots of items to be cleaned, it is hard to see them all
in one screen. Show them in columns will solve this problem.

Signed-off-by: Jiang Xin <worldhello.net@gmail.com>
Comments-by: Matthieu Moy <Matthieu.Moy@imag.fr>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
git-clean: add colors to interactive git-clean

Show header, help, error messages, and prompt in colors for interactive
git-clean. Re-use config variables, such as "color.interactive" and
"color.interactive.<slot>" for command `git-add--interactive`.

Signed-off-by: Jiang Xin <worldhello.net@gmail.com>
Comments-by: Matthieu Moy <Matthieu.Moy@imag.fr>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
git-clean: use a git-add-interactive compatible UI

Rewrite menu using a new method `list_and_choose`, which is borrowed
from `git-add--interactive.perl`. We will use this framework to add
new actions for interactive git-clean later.

Please NOTE:

 * Method `list_and_choose` return an array of integers, and
 * it is up to you to free the allocated memory of the array.
 * The array ends with EOF.
 * If user pressed CTRL-D (i.e. EOF), no selection returned.

Signed-off-by: Jiang Xin <worldhello.net@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
git-clean: add filter by pattern interactive action

Add a new action for interactive git-clean: filter by pattern. When the
user chooses this action, user can input space-separated patterns (the
same syntax as gitignore), and each clean candidate that matches with
one of the patterns will be excluded from cleaning. When the user feels
it's OK, presses ENTER and backs to the confirmation dialog.

Signed-off-by: Jiang Xin <worldhello.net@gmail.com>
Suggested-by: Junio C Hamano <gitster@pobox.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
git-clean: add select by numbers interactive action

Draw a multiple choice menu using `list_and_choose` to select items
to be deleted by numbers.

User can input:

 *  1,5-7 : select 1,5,6,7 items to be deleted
 *  *     : select all items to be deleted
 *  -*    : unselect all, nothing will be deleted
 *        : (empty) finish selecting, and return back to main menu

Signed-off-by: Jiang Xin <worldhello.net@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
git-clean: add ask each interactive action

Add a new action for interactive git-clean: ask each. It's just like
the "rm -i" command, that the user must confirm one by one for each
file or directory to be cleaned.

Signed-off-by: Jiang Xin <worldhello.net@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
git-clean: add documentation for interactive git-clean

Add new section "Interactive mode" for documentation of interactive
git-clean.

Signed-off-by: Jiang Xin <worldhello.net@gmail.com>
Helped-by: Eric Sunshine <sunshine@sunshineco.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
test: add t7301 for git-clean--interactive

Add test cases for git-clean--interactive.

Signed-off-by: Jiang Xin <worldhello.net@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
test: run testcases with POSIX absolute paths on Windows

Some test cases are skipped on Windows by marking with POSIX prereq.
This is because arguments look like absolute paths (such as /a/b)
for regular Windows programs (*.exe executables, no bash scripts)
are changed to Windows paths (like C:/msysgit/a/b).

There is no cygpath nor equivalent on msysGit, but it is easy to
write one. New subcommand "mingw_path" is added in test-path-utils,
so that we can get the expected absolute paths on Windows. E.g.

    COMMAND LINE                        Linux output  Windows output
    ==================================  ============  ===============
    test-path-utils mingw_path /        /             C:/msysgit
    test-path-utils mingw_path /a/b/    /a/b/         C:/msysgit/a/b/

With this utility, most skipped test cases in t0060 can be turned on
to be tested correctly on Windows.

Signed-off-by: Jiang Xin <worldhello.net@gmail.com>