execute, spawn-pipe: Allow caller to specify directory for the subprocess

[Bruno Haible]

It has been noted [1] that when spawning a child process, it is useful to be
able to specify in which directory to execute this child process.

The "obvious" solution, to do a chdir() before spawning the child process
and chdir() or fchdir() back afterwards, has two drawbacks:
  - It is not multithread-safe.
  - It interferes with the search of the program in $PATH, if $PATH contains
    non-absolute directories (which is a bad practice for security reasons
    but not forbidden).

This patch adds a 'directory' parameter to the functions 'execute' and
create_pipe_*.

I need this, in particular, in order to complete the Ruby support for
GNU gettext.

Note the added NEWS entries:

Date        Modules         Changes

2020-12-02  spawn-pipe      The functions 'create_pipe_out', 'create_pipe_in',
                            'create_pipe_bidi' now take a 4th argument
                            'const char *directory'. To maintain the previous
                            behaviour, insert NULL as additional 4th argument.

2020-12-02  execute         The function 'execute' now takes a 4th argument
                            'const char *directory'. To maintain the previous
                            behaviour, insert NULL as additional 4th argument.


[1] https://www.austingroupbugs.net/view.php?id=1208


2020-12-02  Bruno Haible  <bruno@clisp.org>

        spawn-pipe: Allow caller to specify directory for the subprocess.
        * lib/spawn-pipe.h (create_pipe_out, create_pipe_in, create_pipe_bidi):
        Add directory argument.
        * lib/spawn-pipe.c: Include canonicalize.h, filename.h, findprog.h.
        (create_pipe): Add directory argument. If specified, resolve the program
        file name and make it absolute, first. Pass the directory to spawnpvech
        and posix_spawn_file_actions_addchdir.
        (create_pipe_bidi, create_pipe_in, create_pipe_out): Add directory
        argument.
        * modules/spawn-pipe (Depends-on): Add canonicalize, filename,
        findprog-in, posix_spawn, posix_spawn_file_actions_addchdir.
        * tests/test-spawn-pipe-main.c (test_pipe): Update.
        * NEWS: Mention the change.
        * lib/csharpcomp.c (compile_csharp_using_mono,
        compile_csharp_using_sscli): Update.
        * lib/javacomp.c (is_envjavac_gcj, is_envjavac_gcj43, is_gcj_present,
        is_gcj_43): Update.
        * lib/javaversion.c (execute_and_read_line): Update.
        * lib/pipe-filter-gi.c (pipe_filter_gi_create): Update.
        * lib/pipe-filter-ii.c (pipe_filter_ii_execute): Update.

2020-12-02  Bruno Haible  <bruno@clisp.org>

        execute: Allow caller to specify directory for the subprocess.
        * lib/execute.h (execute): Add directory argument.
        * lib/execute.c: Include canonicalize.h, filename.h, findprog.h.
        (execute): Add directory argument. If specified, resolve the program
        file name and make it absolute, first. Pass the directory to spawnpvech
        and posix_spawn_file_actions_addchdir.
        * modules/execute (Depends-on): Add canonicalize, filename, findprog-in,
        posix_spawn, posix_spawn_file_actions_addchdir.
        * tests/test-execute-main.c: Add test for passing a directory.
        * tests/test-execute-child.c: Likewise.
        * tests/test-execute.sh: Update.
        * modules/execute-tests (Depends-on): Add mkdir.
        * NEWS: Mention the change.
        * lib/csharpcomp.c (compile_csharp_using_sscli): Update.
        * lib/csharpexec.c (execute_csharp_using_mono,
        execute_csharp_using_sscli): Update.
        * lib/javacomp.c (compile_using_envjavac, compile_using_gcj,
        compile_using_javac, compile_using_jikes, is_javac_present,
        is_jikes_present): Update.
        * lib/javaexec.c (execute_java_class): Update.

0001-execute-Allow-caller-to-specify-directory-for-the-su.patch
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0002-spawn-pipe-Allow-caller-to-specify-directory-for-the.patch
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