Replace long list by file

The replaces the `strs` list by a corresponding file, which eliminates the need
for looping over the list.

Use sed to transform strings into gettext po format entries.

Format the file with fish_indent and use more expressive variable name for the
file cargo expand writes to.

Performance improvements (in microseconds):
- sort+format rust strings: from 21750 to 11096 (speedup 2.0)

build_tools/fish_xgettext.fish

@@ -15,37 +15,40 @@ begin
     echo ""
 end >$output_file
 
-set -l tmpfile (mktemp)
+set -l cargo_expanded_file (mktemp)
 # This is a gigantic crime.
 # We use cargo-expand to get all our wgettext invocations.
 # This might be replaced once we have a tool which properly handles macro expansions.
-begin cargo expand --lib; for f in fish fish_indent fish_key_reader; cargo expand --bin $f; end; end >$tmpfile
+begin
+    cargo expand --lib
+    for f in fish fish_indent fish_key_reader
+        cargo expand --bin $f
+    end
+end >$cargo_expanded_file
+
+set -l rust_string_file (mktemp)
 
 # Extract any gettext call
-set -l strs (grep -A1 wgettext_static_str <$tmpfile |
-             grep 'widestring::internals::core::primitive::str =' |
-             string match -rg '"(.*)"' | string match -rv '^%ls$|^$' |
-             # escaping difference between gettext and cargo-expand: single-quotes
-             string replace -a "\'" "'")
+grep -A1 wgettext_static_str <$cargo_expanded_file |
+    grep 'widestring::internals::core::primitive::str =' |
+    string match -rg '"(.*)"' |
+    string match -rv '^%ls$|^$' |
+    # escaping difference between gettext and cargo-expand: single-quotes
+    string replace -a "\'" "'" >$rust_string_file
 
 # Extract any constants
-set -a strs (grep -Ev 'BUILD_VERSION:|PACKAGE_NAME' <$tmpfile |
-             grep -E 'const [A-Z_]*: &str = "(.*)"' |
-             sed -E -e 's/^.*const [A-Z_]*: &str = "(.*)".*$/\1/' -e "s_\\\'_'_g")
+grep -Ev 'BUILD_VERSION:|PACKAGE_NAME' <$cargo_expanded_file |
+    grep -E 'const [A-Z_]*: &str = "(.*)"' |
+    sed -E -e 's/^.*const [A-Z_]*: &str = "(.*)".*$/\1/' -e "s_\\\'_'_g" >>$rust_string_file
 
-rm $tmpfile
+rm $cargo_expanded_file
 
 # Sort the extracted strings and remove duplicates.
-# This is optional.
-set -l strs (string join \n -- $strs | sort -u)
+# Then, transform them into the po format
+sort -u $rust_string_file |
+    sed -E 's/^(.*)$/msgid "\1"\nmsgstr ""\n/' >>$output_file
 
-# We construct messages.pot ourselves instead of forcing this into msgmerge or whatever.
-# The escaping so far works out okay.
-for str in $strs
-    echo "msgid \"$str\""
-    echo 'msgstr ""'
-    echo ""
-end >>$output_file
+rm $rust_string_file
 
 function extract_fish_script_messages --argument-names regex
 
@@ -72,7 +75,9 @@ function extract_fish_script_messages --argument-names regex
             string unescape |
             string replace --all '\\' '\\\\' |
             string replace --all '"' '\\"'
-    end | sort -u | string replace --regex '^(.*)$' 'msgid "$1"'\n'msgstr ""'\n >>$output_file
+    end |
+        sort -u |
+        sed -E 's/^(.*)$/msgid "\1"\nmsgstr ""\n/' >>$output_file
 end
 
 # This regex handles explicit requests to translate a message. These are more important to translate