Fix ga, gsp & gcf with older git versions (#335)

Removes the usage of --pathspec-file-nul (which is not available in older git versions) in favor of storing the file names passed to the git command in an array instead of a string.

bin/git-forgit

@@ -342,12 +342,15 @@ _forgit_add() {
         --bind=\"alt-e:execute-silent($FORGIT edit_add_file {})+refresh-preview\"
         $FORGIT_ADD_FZF_OPTS
     "
-    files=$(git -c color.status=always -c status.relativePaths=true status -su |
+    files=()
+    while IFS='' read -r file; do
+        files+=("$file")
+    done < <(git -c color.status=always -c status.relativePaths=true status -su |
         grep -F -e "$changed" -e "$unmerged" -e "$untracked" |
         sed -E 's/^(..[^[:space:]]*)[[:space:]]+(.*)$/[\1]  \2/' |
         FZF_DEFAULT_OPTS="$opts" fzf |
         _forgit_get_single_file_from_add_line)
-    [[ -n "$files" ]] && echo "$files"| tr '\n' '\0' | _forgit_git_add --pathspec-file-nul --pathspec-from-file - && git status -su && return
+    [[ "${#files[@]}" -gt 0 ]] && _forgit_git_add "${files[@]}" && git status -su && return
     echo 'Nothing to add.'
 }
 
@@ -458,9 +461,13 @@ _forgit_stash_push() {
         $FORGIT_STASH_PUSH_FZF_OPTS
     "
     # Show both modified and untracked files
-    files=$(git ls-files --exclude-standard --modified --others | FZF_DEFAULT_OPTS="$opts" fzf --preview="$FORGIT stash_push_preview {}")
-    [[ -z "$files" ]] && return 1
-    echo "${files[@]}" | tr '\n' '\0' | _forgit_git_stash_push ${msg:+-m "$msg"} -u --pathspec-file-nul --pathspec-from-file -
+    files=()
+    while IFS='' read -r file; do
+        files+=("$file")
+    done < <(git ls-files --exclude-standard --modified --others |
+        FZF_DEFAULT_OPTS="$opts" fzf --preview="$FORGIT stash_push_preview {}")
+    [[ "${#files[@]}" -eq 0 ]] && return 1
+    _forgit_git_stash_push ${msg:+-m "$msg"} -u "${files[@]}"
 }
 
 # git clean selector
@@ -651,8 +658,12 @@ _forgit_checkout_file() {
         --preview=\"$FORGIT checkout_file_preview {}\"
         $FORGIT_CHECKOUT_FILE_FZF_OPTS
     "
-    files="$(git ls-files --modified "$(git rev-parse --show-toplevel)"| FZF_DEFAULT_OPTS="$opts" fzf)"
-    [[ -n "$files" ]] && echo "$files" | tr '\n' '\0' | _forgit_git_checkout_file --pathspec-file-nul --pathspec-from-file -
+    files=()
+    while IFS='' read -r file; do
+        files+=("$file")
+    done < <(git ls-files --modified "$(git rev-parse --show-toplevel)" |
+        FZF_DEFAULT_OPTS="$opts" fzf)
+    [[ "${#files[@]}" -gt 0 ]] && _forgit_git_checkout_file "${files[@]}"
 }
 
 _forgit_git_checkout_branch() {