Rename mtt_update to mod_translation_updater (#13952)

Clarifies the purpose of the translation update script by giving it a more explanatory name.

util/README_mod_translation_updater.md

@@ -0,0 +1,213 @@
+# `mod_translation_updater.py`—Minetest Mod Translation Updater
+
+This Python script is intended for use with localized Minetest mods, i.e., mods that use
+`*.tr` and contain translatable strings of the form `S("This string can be translated")`.
+It extracts the strings from the mod's source code and updates the localization files
+accordingly. It can also be used to update the `*.tr` files in Minetest's `builtin` component.
+
+## Preparing your source code
+
+This script makes assumptions about your source code. Before it is usable, you first have
+to prepare your source code accordingly.
+
+### Choosing the textdomain name
+
+It is recommended to set the textdomain name (for `minetest.get_translator`) to be identical
+of the mod name as the script will automatically detect it. If the textdomain name differs,
+you may have to manually change the `# textdomain:` line of newly generated files.
+
+**Note:** In each `*.tr` file, there **must** be only one textdomain. Multiple textdomains in
+the same file are not supported by this script and any additional textdomain line will be
+removed.
+
+### Defining the helper functions
+
+In any source code file with translatable strings, you have to manually define helper
+functions at the top with something like `local S = minetest.get_translator("<textdomain>")`.
+Optionally, you can also define additional helper functions `FS`, `NS` and `NFS` if needed.
+
+Here is the list of all recognized function names. All functions return a string.
+
+* `S`: Returns translation of input. See Minetest's `lua_api.md`. You should always have at
+       least this function defined.
+* `NS`: Returns the input. Useful to make a string visible to the script without actually
+        translating it here.
+* `FS`: Same as `S`, but returns a formspec-escaped version of the translation of the input.
+        Supported for convenience.
+* `NFS`: Returns a formspec-escaped version of the input, but not translated.
+         Supported for convenience.
+
+Here is the boilerplate code you have to add at the top of your source code file:
+
+    local S = minetest.get_translator("<textdomain>")
+    local NS = function(s) return s end
+    local FS = function(...) return minetest.formspec_escape(S(...)) end
+    local NFS = function(s) return minetest.formspec_escape(s) end
+
+Replace `<textdomain>` above and optionally delete `NS`, `FS` and/or `NFS` if you don't need
+them.
+
+### Preparing the strings
+
+This script can detect translatable strings of the notations listed below.
+Additional function arguments followed after a literal string are ignored.
+
+* `S("literal")`: one literal string enclosed by the delimiters
+  `"..."`, `'...'` or `[[...]]`
+* `S("foo " .. 'bar ' .. "baz")`: concatenation of multiple literal strings. Line
+  breaks are accepted.
+
+The `S` may also be `NS`, `FS` and `NFS` (see above).
+
+Undetectable notations:
+
+* `S"literal"`: omitted function brackets
+* `S(variable)`: requires the use of `NS`. See example below.
+* `S("literal " .. variable)`: non-static content.
+  Use placeholders (`@1`, ...) for variable text.
+* Any literal string concatenation using `[[...]]`
+
+### A minimal example
+
+This minimal code example sends "Hello world!" to all players, but translated according to
+each player's language:
+
+    local S = minetest.get_translator("example")
+    minetest.chat_send_all(S("Hello world!"))
+
+### How to use `NS`
+
+The reason why `NS` exists is for cases like this: Sometimes, you want to define a list of
+strings to they can be later output in a function. Like so:
+
+    local fruit = { "Apple", "Orange", "Pear" }
+    local function return_fruit(fruit_id)
+       return fruit[fruit_id]
+    end
+
+If you want to translate the fruit names when `return_fruit` is run, but have the
+*untranslated* fruit names in the `fruit` table stored, this is where `NS` will help.
+It will show the script the string without Minetest translating it. The script could be made
+translatable like this:
+
+    local fruit = { NS("Apple"), NS("Orange"), NS("Pear") }
+    local function return_fruit(fruit_id)
+       return S(fruit[fruit_id])
+    end
+
+## How to run the script
+
+First, change the working directory to the directory of the mod you want the files to be
+updated. From this directory, run the script.
+
+When you run the script, it will update the `template.txt` and any `*.tr` files present
+in that mod's `/locale` folder. If the `/locale` folder or `template.txt` file don't
+exist yet, they will be created.
+
+This script will also work in the root directory of a modpack. It will run on each mod
+inside the modpack in that situation. Alternatively, you can run the script to update
+the files of all mods in subdirectories with the `-r` option, which is useful to update
+the locale files in an entire game.
+
+It has the following command line options:
+
+    mod_translation_updater.py [OPTIONS] [PATHS...]
+
+    --help, -h: prints this help message
+    --recursive, -r: run on all subfolders of paths given
+    --old-file, -o: create copies of files before updating them, named `<FILE NAME>.old`
+    --break-long-lines, -b: add extra line-breaks before and after long strings
+    --print-source, -p: add comments denoting the source file
+    --verbose, -v: add output information
+    --truncate-unused, -t: delete unused strings from files
+
+## Script output
+
+This section explains how the output of this script works, roughly. This script aims to make
+the output more or less stable, i.e. given identical source files and arguments, the script
+should produce the same output.
+
+### Textdomain
+
+The script will add (if not already present) a `# textdomain: <modname>` at the top, where
+`<modname>` is identical to the mod directory name. If a `# textdomain` already exists, it
+will be moved to the top, with the textdomain name being left intact (even if it differs
+from the mod name).
+
+**Note:** If there are multiple `# textdomain:` lines in the file, all of them except the
+first one will be deleted. This script only supports one textdomain per `*.tr` file.
+
+### Strings
+
+The order of the strings is deterministic and follows certain rules: First, all strings are
+grouped by the source `*.lua` file. The files are loaded in alphabetical order. In case of
+subdirectories, the mod's root directory takes precedence, then the directories are traversed
+in top-down alphabetical order. Second, within each file, the strings are then inserted in
+the same order as they appear in the source code.
+
+If a string appears multiple times in the source code, the string will be added when it was
+first found only.
+
+Don't bother to manually organize the order of the lines in the file yourself because the
+script will just reorder everything.
+
+If the mod's source changes in such a way that a line with an existing translation or comment
+is no longer present, and `--truncate-unused` or `-t` are *not* provided as arguments, the
+unused line will be moved to the bottom of the translation file under a special comment:
+
+    ##### not used anymore #####
+
+This allows for old translations and comments to be reused with new lines where appropriate.
+This script doesn't attempt "fuzzy" matching of old strings to new, so even a single change
+of punctuation or spelling will put strings into the "not used anymore" section and require
+manual re-association with the new string.
+
+### Comments
+
+The script will preserve any comments in an existing `template.txt` or the various `*.tr`
+files, associating them with the line that follows them. So for example:
+
+    # This comment pertains to Some Text
+    Some text=
+    
+    # Multi-line comments
+    # are also supported
+    Text as well=
+
+There are also a couple of special comments that this script gives special treatment to.
+
+#### Source file comments
+
+If `--print-source` or `-p` is provided as option, the script will insert comments to show
+from which file or files each string has come from.
+This is the syntax of such a comment:
+
+    ##[ file.lua ]##
+
+This comment means that all lines following it belong to the file `file.lua`. In the special
+case the same string was found in multiple files, multiple file name comments will be used in
+row, like so:
+
+    ##[ file1.lua ]##
+    ##[ file2.lua ]##
+    ##[ file3.lua ]##
+    example=Beispiel
+
+This means the string "example" was found in the files `file1.lua`, `file2.lua` and
+`file3.lua`.
+
+If the print source option is not provided, these comments will disappear.
+
+Note that all comments of the form `##[something]##` will be treated as "source file" comments
+so they may be moved, changed or removed by the script at will.
+
+#### "not used anymore" section
+
+By default, the exact comment `##### not used anymore #####` will be automatically added to
+mark the beginning of a section where old/unused strings will go. Leave the exact wording of
+this comment intact so this line can be moved (or removed) properly in subsequent runs.
+
+## Updating `builtin`
+
+To update the `builtin` component of Minetest, change the working directory to `builtin` of
+the Minetest source code repository, then run this script from there.