Merge branch 'js/fix-open-exec-git'

Merge branch 'js/fix-open-exec-git'

This addresses CVE-2025-46835, Git GUI can create and overwrite a
user's files:

When a user clones an untrusted repository and is tricked into editing
a file located in a maliciously named directory in the repository, then
Git GUI can create and overwrite files for which the user has write
permission.

* js/fix-open-exec-git:
  git-gui: sanitize 'exec' arguments: convert new 'cygpath' calls
  git-gui: do not mistake command arguments as redirection operators
  git-gui: introduce function git_redir for git calls with redirections
  git-gui: pass redirections as separate argument to git_read
  git-gui: pass redirections as separate argument to _open_stdout_stderr
  git-gui: convert git_read*, git_write to be non-variadic
  git-gui: use git_read in githook_read
  git-gui: break out a separate function git_read_nice
  git-gui: remove option --stderr from git_read
  git-gui: sanitize 'exec' arguments: background
  git-gui: sanitize 'exec' arguments: simple cases
  git-gui: treat file names beginning with "|" as relative paths
  git-gui: remove git config --list handling for git < 1.5.3
  git-gui: remove HEAD detachment implementation for git < 1.5.3
  git-gui: remove Tcl 8.4 workaround on 2>@1 redirection

Signed-off-by: Johannes Sixt <j6t@kdbg.org>