X-Git-Url: https://git.ladys.computer/Shushe/blobdiff_plain/e7c797ffb120c0dac9be13b28d533d49d164b6d0..5df1b342a607db60d876eeb10d953b7a45464e24:/README.markdown

diff --git a/README.markdown b/README.markdown
index 2dd0eff..2cefb62 100644
--- a/README.markdown
+++ b/README.markdown
@@ -1,6 +1,10 @@
+<!--
+SPDX-FileCopyrightText: 2024 Lady <https://www.ladys.computer/about/#lady>
+SPDX-License-Identifier: CC0-1.0
+-->
 # ⛩️📰 书社
 
-<b>An X·S·L·T‐based static site generator.</b>
+<b>A make·file for X·M·L.</b>
 
 <dfn>⛩️📰 书社</dfn> aims to make it easy to generate websites with
   X·S·L·T and G·N·U Make.
@@ -17,7 +21,12 @@ It makes things easier by :⁠—
 - Enabling easy inclusion of source files within each other.
 
 It aims to do this with zero dependencies beyond the programs already
-  installed on your computer.
+  installed on your computer†.
+
+† Assuming an operating system with a fairly featureful, and
+  Posix‐compliant, development setup (e·g, Macintosh ≥ version 10.8).
+In fact, on Linux you will probably need to install a few programs:
+  `libxml2-utils`, `xsltproc`, `sharutils`, and `pax`.
 
 ## Nomenclature
 
@@ -39,6 +48,98 @@ The name <i lang="cmn-Hans">书社</i> was chosen to play on this pun, as
 In Ascii environments, ⛩️📰 书社 should be written `Shushe`, following
   the pinyin transliteration.
 
+## Prerequisites
+
+In most cases, ⛩️📰 书社 aims to require only functionality which is
+  present in all Posix‐compliant (`POSIX.1-2001`) operating systems.
+There are a few exceptions.
+Details on particular programs are given below; if a program is not
+  listed, it is assumed that any Posix‐compliant implementation will
+  work.
+
+### `diff`
+
+This is a Posix utility, but ⛩️📰 书社 depends on functionality
+  introduced after `POSIX.1-2001` (the `-u` option, introduced in
+  `POSIX.1-2008`).
+Macintosh systems somewhat interestingly implement this option
+  correctly in legacy mode (`COMMAND_MODE=legacy`) but incorrectly by
+  default (despite claiming `POSIX.1-2008` conformance for this
+  utility).
+[Note this erroneous comment claiming nanosecond & timezone are
+  extensions rather than standardized.][rdar-92753335]
+Despite this, the default Macintosh implementation will still work with
+  ⛩️📰 书社, with the caveat that the timestamp will only include a
+  fractional component when a Posix⹀compliant (e·g, Macintosh legacy or
+  G·N·U) implementation is used.
+
+### `file`
+
+This is a Posix utility, but it was considered optional in
+  `POSIX.1-2001` (altho it was made mandatory in `POSIX.1-2008`) and
+  ⛩️📰 书社 currently depends on unspecified behaviour.
+It requires support for the following additional options :⁠—
+
+- **`-C`**, when supplied with `-m`, must be useable to compile a
+    `.mgc` magicfile for use with future invocations of `file`.
+
+- **`--files-from`** must be useable to provide a file that `file`
+    should read file·names from, and `-` must be useable in this
+    context to specify the standard input.
+
+- **`--mime-type`** must cause `file` to print the internet media type
+    of the file with no charset parameter.
+
+- **`--separator`** must be useable to set the separator that `file`
+    uses to separate file names from types.
+
+These options are implemented by the
+  [Fine Free File Command](https://darwinsys.com/file/), which is used
+  by most operating systems.
+
+### `git`
+
+This is not a Posix utility.
+Usage of `git` is optional, but recommended (and activated by default).
+To disable it, set `GIT=`.
+
+### `make`
+
+This is a Posix utility, but it is considered an optional Software
+  Development utility and ⛩️📰 书社 currently depends on unspecified
+  behaviour.
+⛩️📰 书社 requires specifically the G·N·U version of `make`, and
+  depends on functionality present in version 3.81 or later.
+It is not expected to work in previous versions, or with other
+  implementations of Make.
+
+### `pax`
+
+This is a Posix utility, but it is not included in the Linux Standard
+  Base or installed by default in many distributions.
+⛩️📰 书社 only requires support for the `ustar` format.
+
+### `uudecode` and `uuencode`
+
+These are Posix utilities, but they were considered optional in
+  `POSIX.1-2001` (altho they are made mandatory in `POSIX.1-2008`) and
+  they are not included in the Linux Standard Base or installed by
+  default in many distributions.
+The G·N·U [Sharutils](https://www.gnu.org/software/sharutils/) package
+  provides one implementation.
+
+### `xmlcatalog` and `xmllint`
+
+These are not a Posix utilities.
+They are a part of `libxml2`, but may need to be installed separately
+  on some platforms (e·g by the name `libxml2-utils`).
+
+### `xsltproc`
+
+This is not a Posix utility.
+It is a part of `libxslt`, but may need to be installed separately on
+  some platforms.
+
 ## Basic Usage
 
 Place source files in `sources/` and run `make install` to compile
@@ -60,9 +161,13 @@ Compilation involves the following steps :⁠—
 5. ⛩️📰 书社 uses the dependency tree to establish prerequisites for
     each output file.
 
-6. ⛩️📰 书社 compiles each output file to `build/public`.
+6. ⛩️📰 书社 compiles each output file to `build/result`.
 
-7. ⛩️📰 书社 copies the output files to `public`.
+7. ⛩️📰 书社 copies most output files from `build/result` to
+     `build/public`, but it does some additional processing instead on
+     those which indicate a non‐X·M·L desired final output form.
+
+8. ⛩️📰 书社 copies the final resulting files to `public`.
 
 You can use `make list` to list each identified source file or include
   alongside its computed type and dependencies.
@@ -70,19 +175,23 @@ As this is a Make‐based program, steps will only be run if the
   corresponding buildfile or output file is older than its
   prerequisites.
 
-## Namespaces
+## Name·spaces
 
-The ⛩️📰 书社 namespace is `urn:fdc:ladys.computer:20231231:Shu1She4`.
+The ⛩️📰 书社 name·space is `urn:fdc:ladys.computer:20231231:Shu1She4`.
 
-This document uses a few namespace prefixes, with the following
+This document uses a few name·space prefixes, with the following
   meanings :⁠—
 
-|   Prefix | Expansion                                  |
-| -------: | :----------------------------------------- |
-|  `html:` | `http://www.w3.org/1999/xhtml`             |
-| `xlink:` | `http://www.w3.org/1999/xlink`             |
-|  `xslt:` | `http://www.w3.org/1999/XSL/Transform`     |
-|  `书社:` | `urn:fdc:ladys.computer:20231231:Shu1She4` |
+|     Prefix | Expansion                                     |
+| ---------: | :-------------------------------------------- |
+| `catalog:` | `urn:oasis:names:tc:entity:xmlns:xml:catalog` |
+|    `exsl:` | `http://exslt.org/common`                     |
+| `exslstr:` | `http://exslt.org/strings`                    |
+|    `html:` | `http://www.w3.org/1999/xhtml`                |
+|     `svg:` | `http://www.w3.org/2000/svg`                  |
+|   `xlink:` | `http://www.w3.org/1999/xlink`                |
+|    `xslt:` | `http://www.w3.org/1999/XSL/Transform`        |
+|    `书社:` | `urn:fdc:ladys.computer:20231231:Shu1She4`    |
 
 ## Setup and Configuration
 
@@ -91,21 +200,32 @@ In every case, you may supply your own implementation by overriding the
   corresponding (allcaps) variable (e·g, set `MKDIR` to supply your own
   `mkdir` implementation).
 
+- `awk`
 - `cat`
+- `cd`
+- `cksum`
 - `cp`
-- `echo`
+- `date`
+- `diff`
 - `file`
 - `find`
-- `mkdir` (requires support for `-p`)
+- `git` (optional; set `GIT=` to disable)
+- `grep`
+- `ln`
+- `mkdir`
 - `mv`
+- `od`
+- `pax` (only when generating archives)
 - `printf`
 - `rm`
 - `sed`
 - `sleep`
 - `test`
 - `touch`
-- `tr` (requires support for `-d`)
-- `uuencode` (requires support for `-m` and `-r`)
+- `tr`
+- `uuencode`
+- `uudecode`
+- `xargs`
 - `xmlcatalog` (provided by `libxml2`)
 - `xmllint` (provided by `libxml2`)
 - `xsltproc` (provided by `libxslt`)
@@ -115,16 +235,32 @@ The following additional variables can be used to control the behaviour
 
 - **`SRCDIR`:**
   The location of the source files (default: `sources`).
+  Multiple source directories can be provided, so long as the same
+    file subpath doesn’t exist in more than one of them.
 
 - **`INCLUDEDIR`:**
-  The location of the source files (default: `sources/includes`).
+  The location of source includes (default: `sources/includes`).
   This can be inside of `SRCDIR`, but needn’t be.
+  Multiple include directories can be provided, so long as the same
+    file subpath doesn’t exist in more than one of them.
 
 - **`BUILDDIR`:**
   The location of the (temporary) build directory (default: `build`).
+  `make clean` will delete this, and it is recommended that it not be
+    used for programs aside from ⛩️📰 书社.
 
 - **`DESTDIR`:**
   The location of directory to output files to (default: `public`).
+  `make install` will overwrite files in this directory which
+    correspond to those in `SRCDIR`.
+  It *will not* touch other files, including those generated from files
+    in `SRCDIR` which have since been deleted.
+
+  Files are first compiled to `$(BUILDDIR)/public` before they are
+    copied to `DESTDIR`, so this folder is relatively quick and
+    inexpensive to re·create.
+  It’s reasonable to simply delete it before every `make install` to
+    ensure stale content is removed.
 
 - **`THISDIR`:**
   The location of the ⛩️📰 书社 `GNUmakefile`.
@@ -133,28 +269,70 @@ The following additional variables can be used to control the behaviour
   This variable is used to find the ⛩️📰 书社 `lib/` folder, which is
     expected to be in the same location.
 
-- **`MAGICDIR`:**
-  The location of the magic files to use (default: `$(THISDIR)/magic`).
+- **`MAGIC`:**
+  A white·space‐separated list of magic files to use (default:
+    `$(THISDIR)/magic/*`).
 
-- **`FINDOPTS`:**
-  Options to pass to `find` when searching for source files (default:
-    `-LE`).
+- **`EXTRAMAGIC`:**
+  The value of this variable is appended to `MAGIC` by default, to
+    enable additional magic files without overriding the existing ones.
 
 - **`FINDRULES`:**
-  Rules to use with `find` when searching for source files (default:
-    `-flags -nohidden -and -not -name '.*'`).
+  Rules to use with `find` when searching for source files.
+  The default ignores files that start with a period or hyphen‐minus,
+    those which end with a cloparen, and those which contain a hash,
+    buck, percent, asterisk, colon, semi, eroteme, bracket, backslash,
+    or pipe.
+
+- **`EXTRAFINDRULES`:**
+  The value of this variable is appended to `FINDRULES` by default, to
+    enable additional rules without overriding the existing ones.
+
+- **`FINDINCLUDERULES`:**
+  Rules to use with `find` when searching for includes (default:
+    `$(FINDRULES)`).
+
+- **`EXTRAFINDINCLUDERULES`:**
+  The value of this variable is appended to `FINDINCLUDERULES` by
+    default, to enable additional rules without overriding the existing
+    ones.
 
 - **`PARSERS`:**
   A white·space‐separated list of parsers to use (default:
     `$(THISDIR)/parsers/*.xslt`).
 
+- **`EXTRAPARSERS`:**
+  The value of this variable is appended to `PARSERS` by default, to
+    enable additional parsers without overriding the existing ones.
+
 - **`TRANSFORMS`:**
   A white·space‐separated list of transforms to use (default:
     `$(THISDIR)/transforms/*.xslt`).
 
+- **`EXTRATRANSFORMS`:**
+  The value of this variable is appended to `TRANSFORMS` by default, to
+    enable additional transforms without overriding the existing ones.
+
 - **`XMLTYPES`:**
-  A white·space‐separated list of media types to consider X·M·L
-    (default: `application/xml text/xml`).
+  A white·space‐separated list of media types or media type suffixes to
+    consider X·M·L (default: `application/xml text/xml +xml`).
+
+- **`THISREV`:**
+  The current version of ⛩️📰 书社 (default: derived from the current
+    git tag/branch/commit).
+
+- **`SRCREV`:**
+  The current version of the source files (default: derived from the
+    current git tag/branch/commit).
+
+- **`QUIET`:**
+  If this variable has a value, informative messages will not be
+    printed (default: empty).
+  Informative messages print to stderr, not stdout, so disabling them
+    usually shouldn’t be necessary.
+  This does not (cannot) disable messages from Make itself, for which
+    the `-s`, `--silent` ∕ `--quiet` Make option is more likely to be
+    useful.
 
 - **`VERBOSE`:**
   If this variable has a value, every recipe instruction will be
@@ -175,6 +353,8 @@ Supported magic numbers include :⁠—
 - `#!js` for `text/javascript` files
 - `@charset "` for `text/css` files
 - `#!tsv` for `text/tab-separated-values` files
+- `%%` for `text/record-jar` files (unregistered; see
+    [[draft-phillips-record-jar-01][]])
 
 Text formats with associated X·S·L·T parsers are wrapped in a H·T·M·L
   `<script>` element whose `@type` gives its media type, and then
@@ -182,18 +362,16 @@ Text formats with associated X·S·L·T parsers are wrapped in a H·T·M·L
 Source files whose media type does not have an associated X·S·L·T
   parser are considered “assets” and will not be transformed.
 
-For compatibility with this program, source filenames should conform to
-  the following rules :⁠—
-
-- They should not start with a hyphen‐minus.
-  This is to prevent confusion between filenames and options on the
-    commandline.
-
-- They should not contain spaces, colons, percent signs, backticks,
-    question marks, hashes, or backslashes.
-
-In general, filenames should be such that they do not require
-  percent‐encoding in the path component of an i·r·i.
+**☡ For compatibility with this program, source file·names must not
+  contain Ascii white·space, colons (`:`), semis (`;`), pipes (`|`),
+  bucks (`$`), percents (`%`), hashes (`#`), asterisks (`*`), brackets
+  (`[` or `]`), erotemes (`?`), backslashes (`\`), or control
+  characters, must not begin with a hyphen‐minus (`-`), and must not end
+  with a cloparen (`)`).**
+The former characters have the potential to conflict with make syntax,
+  a leading hyphen‐minus is confusable for a commandline argument, and a
+  trailing cloparen [activates a bug in G·N·U Make
+  3.81](https://stackoverflow.com/questions/17148468/capturing-filenames-including-parentheses-with-gnu-makes-wildcard-function#comment24825307_17148894).
 
 ## Parsers
 
@@ -205,14 +383,19 @@ Parsers are used to convert plaintext files into X·M·L trees, as well
 - **`parsers/plain.xslt`:**
   Wraps `text/plain` contents in a `<html:pre>` element.
 
+- **`parsers/record-jar.xslt`:**
+  Converts `text/record-jar` contents into a `<html:div>` of
+    `<html:dl>` elements (one for each record).
+
 - **`parsers/tsv.xslt`:**
   Converts `text/tab-separated-values` contents into an `<html:table>`
     element.
 
-New ⛩️📰 书社 parsers should have a `<xslt:template>` element with no
-  `@name` or `@mode` and whose `@match` attribute…
+New ⛩️📰 书社 parsers which target plaintext formats should have an
+  `<xslt:template>` element with no `@name` or `@mode` and whose
+  `@match` attribute…
 
-- Starts with an appropriately‐namespaced qualified name for a
+- Starts with an appropriately‐name·spaced qualified name for a
     `<html:script>` element.
 
 - Follows this with the string `[@type=`.
@@ -228,13 +411,15 @@ For example, the trivial `text/plain` parser is defined as follows :⁠—
 ```xml
 <?xml version="1.0"?>
 <transform
-	xmlns="http://www.w3.org/1999/XSL/Transform"
-	xmlns:html="http://www.w3.org/1999/xhtml"
-	version="1.0"
+  xmlns="http://www.w3.org/1999/XSL/Transform"
+  xmlns:html="http://www.w3.org/1999/xhtml"
+  xmlns:书社="urn:fdc:ladys.computer:20231231:Shu1She4"
+  version="1.0"
 >
-	<template match="html:script[@type='text/plain']">
-		<html:pre><value-of select="."/></html:pre>
-	</template>
+  <书社:id>example:text/plain</书社:id>
+  <template match="html:script[@type='text/plain']">
+    <html:pre><value-of select="."/></html:pre>
+  </template>
 </transform>
 ```
 
@@ -242,10 +427,53 @@ For example, the trivial `text/plain` parser is defined as follows :⁠—
   the set of allowed plaintext file types.
 Multiple such `<xslt:template>` elements may be provided in a single
   parser, for example if the parser supports multiple media types.
-
-It is **strongly recommended** that all templates in parsers other than
-  those described above be namespaced (by `@name` or `@mode`), to avoid
-  conflicts between templates in multiple parsers.
+Alternatively, you can set the `@书社:supported-media-types` attribute
+  on the root element of the parser to override media type support
+  detection.
+
+Even when `@书社:supported-media-types` is set, it is a requirement
+  that each parser transform any `<html:script>` elements with a
+  `@type` which matches their registered types into something else.
+Otherwise the parser will be stuck in an endless loop.
+The result tree of applying the transform to the `<html:script>`
+  element will be reparsed (in case any new `<html:script>` elements
+  were added in its subtree), and a `@书社:parsed-by` attribute will be
+  added to each toplevel element in the result.
+The value of this attribute will be the value of the `<书社:id>`
+  toplevel element in the parser.
+
+It is possible for parsers to support zero plaintext types.
+This is useful when targeting specific dialects of X·M·L; parsers in
+  this sense operate on the same basic principles as transforms
+  (described below).
+The major distinction between X·M·L parsers and transforms is where in
+  the process the transformation happens:
+Parsers are applied *prior* to embedding (and can be used to generate
+  embeds); transforms are applied *after*.
+
+It is **strongly recommended** that auxillary templates in parsers be
+  name·spaced (by `@name` or `@mode`) whenever possible, to avoid
+  conflicts between parsers.
+
+### Attributes added during parsing
+
+⛩️📰 书社 will add a few attributes to the output of the parsing step,
+  namely :⁠—
+
+- A `@书社:cksum` attribute on toplevel result elements, giving the
+    `cksum` checksum of the corresponding source file.
+
+- For the elements which result from parsing plaintext `<html:script>`
+    elements :⁠—
+
+  - A `@书社:parsed-by` attribute, giving a space‐separated list of
+      parsers which parsed the node.
+    (Generally, this will be a list of one, but it is possible for the
+      result of a parse to be another plaintext node, which may be
+      parsed by a different parser.)
+
+  - A `@书社:media-type` attribute, giving the identified media type of
+      the plaintext node.
 
 ## Embedding
 
@@ -263,6 +491,8 @@ Embeds are replaced with the parsed contents of a file, unless the file
   is an asset, in which case an `<html:object>` element is produced
   instead (with the contents of the asset file provided as a base64
   `data:` u·r·i).
+Embed replacements will be given a `@书社:identifier` attribute whose
+  value will match the `@xlink:href` of the embed.
 
 Embedding takes place after parsing but before transformation, so
   parsers are able to generate their own embeds.
@@ -270,6 +500,15 @@ Embedding takes place after parsing but before transformation, so
   and update them accordingly; it will signal an error if the
   dependencies are recursive.
 
+## Output Redirection
+
+By default, ⛩️📰 书社 installs files to the same location in `DESTDIR`
+  as they were placed in their `SRCDIR`.
+This behaviour can be customized by setting the `@书社:destination`
+  attribute on the root element, whose value can give a different path.
+This attribute is read after parsing, but before transformation (where
+  it is silently dropped).
+
 ## Transforms
 
 Transforms are used to convert X·M·L files into their final output,
@@ -277,25 +516,51 @@ Transforms are used to convert X·M·L files into their final output,
 ⛩️📰 书社 comes with some transforms; namely :⁠—
 
 - **`transforms/asset.xslt`:**
-  Converts `<html:object type="text/css">` elements into corresponding
-    `<html:link rel="stylesheet">` elements and
-    `<html:object type="text/javascript">` elements into corresponding
-    `<html:script>` elements.
-  This transform enables embedding of `text/css` and `text/javascript`
-    files, which ordinarily are considered assets (as they lack
-    associated parsers).
+  Converts `<html:object>` elements which correspond to recognized
+    media types into the appropriate H·T·M·L elements, and deletes
+    `<html:style>` elements from the body of the document and moves
+    them to the head.
 
 - **`transforms/metadata.xslt`:**
   Provides basic `<html:head>` metadata.
-  This metadata is generated from `<html:meta>` descendants of the
-    first element with an `@itemscope` attribute (recommended to just
-    be the root element).
-  Such elements can provide metadata using the following `@itemprop`
-    attributes :⁠—
+  This metadata is generated from `<html:meta>` elements with one of
+    the following `@itemprop` attributes :⁠—
 
   - **`urn:fdc:ladys.computer:20231231:Shu1She4:title`:**
     Provides the title of the page.
 
+  ⛩️📰 书社 automatically encapsulates H·T·M·L embeds so that their
+    metadata does not propogate up to the embedding document.
+  To undo this behaviour, remove the `@itemscope` and `@itemtype`
+    attributes from the embed during the transformation phase.
+
+- **`transforms/serialization.xslt`:**
+  Replaces `<书社:serialize-xml>` elements with the (escaped)
+    serialized X·M·L of their contents.
+  This replacement happens during the application phase, after most
+    other transformations have taken place.
+
+  If a `@with-namespaces` attribute is provided, any name·space nodes
+    on the toplevel serialized elements whose U·R·I’s correspond to the
+    definitions of the provided prefixes, as defined for the
+    `<书社:serialize-xml>` element, will be declared using name·space
+    attributes on the serialized elements.
+  Otherwise, only name·space nodes which _differ_ from the definitions
+    on the `<书社:serialize-xml>` element will be declared.
+  The string `#default` may be used to represent the default
+    name·space.
+  Multiple prefixes may be provided, separated by white·space.
+
+  When it comes to name·spaces used internally by ⛩️📰 书社, the
+    prefix used by ⛩️📰 书社 may be declared _in addition to_ the
+    prefix(es) used in the source document(s).
+  It is not possible to selectively only declare one prefix for a
+    name·space to the exclusion of others.
+
+  `<书社:raw-output>` elements may be used inside of
+    `<书社:serialize-xml>` elements to inject raw output into the
+    serialized X·M·L.
+
 The following are recommendations on effective creation of
   transforms :⁠—
 
@@ -303,23 +568,159 @@ The following are recommendations on effective creation of
   It is likely an error if two transforms have templates which match
     the same element (unless the templates have different priority).
 
-- Namespace templates (with `@name` or `@mode`) whenever possible.
+- Name·space templates (with `@name` or `@mode`) whenever possible.
 
 - Set `@exclude-result-prefixes` on the root `xslt:transform` element
-    to reduce the number of declared namespaces in the final result.
+    to reduce the number of declared name·spaces in the final result.
+
+## Global Params
+
+The following params are made available globally in parsers and
+  transforms :⁠—
+
+- **`BUILDTIME`:**
+  The current time.
+
+- **`CKSUM`:**
+  The checksum of the source file (⅌ `cksum`).
+
+- **`IDENTIFIER`:**
+  The ⛩️📰 书社 identifier of the source file (a u·r·i beginning with
+    `about:shushe`).
+
+- **`SRCREV`:**
+  The value of the `SRCREV` variable (if present).
+
+- **`SRCTIME`:**
+  The time at which the source file was last modified.
+
+- **`THISREV`:**
+  The value of the `THISREV` variable (if present).
+
+The following params are only available in transforms :⁠—
+
+- **`CATALOG`:**
+  The path of the catalog file (within `BUILDDIR`).
+
+- **`PATH`:**
+  The path of the output file (within `DESTDIR`).
 
 ## Output Wrapping
 
 ⛩️📰 书社 will wrap the final output of the transforms in appropriate
   `<html:html>` and `<html:body>` elements, so it is not necessary for
   transforms to do this explicitly.
-The `<html:head>` of the output will contain the result tree generated
-  by matching the root node in the `书社:metadata` mode; the provided
-  `transforms/metadata.xslt` transform uses this mode to generate basic
-  metadata, but it is possible for other transforms to add their own.
+After performing the initial transform, ⛩️📰 书社 will match the root
+  node of the result in the following modes to fill in areas of the
+  wrapper :⁠—
+
+- **`书社:header`:**
+  The result of matching in this mode is prepended into the
+    `<html:body>` of the output (before the transformation result).
+
+- **`书社:footer`:**
+  The result of matching in this mode is appended into the
+    `<html:body>` of the output (after the transformation result).
+
+- **`书社:metadata`:**
+  The result of matching in this mode is inserted into the
+    `<html:head>` of the output.
+
+In addition to being called with the transform result, each of these
+  modes will additionally be called with a `<xslt:include>` element
+  corresponding to each transform.
+If a transform has a `<书社:id>` top‐level element whose value is an
+  i·r·i, its `<xslt:include>` element will have a corresponding
+  `@书社:id` attribute.
+This mechanism can be used to allow transforms to insert content
+  without matching any elements in the result; for example, the
+  following transform adds a link to a stylesheet to the `<html:head>`
+  of every page :⁠—
+
+```xml
+<?xml version="1.0"?>
+<transform
+  xmlns="http://www.w3.org/1999/XSL/Transform"
+  xmlns:html="http://www.w3.org/1999/xhtml"
+  xmlns:xslt="http://www.w3.org/1999/XSL/Transform"
+  xmlns:书社="urn:fdc:ladys.computer:20231231:Shu1She4"
+  exclude-result-prefixes="书社"
+  version="1.0"
+>
+  <书社:id>example:add-stylesheet-links.xslt</书社:id>
+  <template match="xslt:include[@书社:id='example:add-stylesheet-links.xslt']" mode="书社:metadata">
+    <html:link rel="stylesheet" type="text/css" href="/style.css"/>
+  </template>
+</transform>
+```
+
+Output wrapping can be entirely disabled by adding a
+  `@书社:disable-output-wrapping` attribute to the top‐level element in
+  the result tree.
+It will not be performed on outputs whose root elements are
+  `<书社:archive>`, `<书社:base64-binary>`, or `<书社:raw-text>`
+  (described below).
+
+## Applying Attributes
+
+The `<书社:apply-attributes>` element will apply any attributes on the
+  element to the element(s) it wraps.
+It is especially useful in combination with embeds.
+
+The `<书社:apply-attributes-to-root>` element will apply any attributes
+  on the element to the root node of the final transformation result.
+It is especially useful in combination with output wrapping.
+
+In both cases, attributes from various sources are combined with
+  white·space between them.
+Attribute application takes place after all ordinary transforms have
+  completed.
+
+Both elements ignore attributes in the `xml:` name·space, except for
+  `@xml:lang`, which ignores all but the first definition (including
+  any already present on the root element).
+On H·T·M·L and S·V·G elements, `@lang` has the same behaviour as
+  `@xml:lang`.
+
+## Other Kinds of Output
+
+There are a few special elements in the `书社:` name·space which, if
+  they appear as the toplevel element in a transformation result, cause
+  ⛩️📰 书社 to produce something other than an X·M·L file.
+They are :⁠—
+
+- **`<书社:archive>`:**
+  Each child element with a `@书社:archived-as` attribute will be
+    archived as a separate file in a resulting tarball (this attribute
+    gives the file name).
+  These elements will be processed the same as the root elements of any
+    other file (e·g, they will be wrapped; they can themselves specify
+    non X·M·L output types, ⁊·c).
+  Other child elements will be ignored.
+
+  If the `<书社:archive>` element is given an `@书社:expanded`
+    attribute, rather than producing a tarball ⛩️📰 书社 will output
+    the directory which expanding the tarball would produce.
+  This mechanism can be used to generate multiple files from a single
+    source, provided all of the files are contained with·in the same
+    directory.
+
+- **`<书社:base64-binary>`:**
+  The text nodes in the transformation result will, after removing all
+    Ascii whitespace, be treated as a Base·64 string, which is then
+    decoded.
+
+- **`<书社:raw-text>`:**
+  A plaintext (U·T·F‐8) file will be produced from the text nodes in
+    the transformation result.
 
 ## License
 
-Source files are licensed under the terms of the <cite>Mozilla Public
-  License, version 2.0</cite>.
-For more information, see [LICENSE](./LICENSE).
+This repository conforms to [REUSE][].
+
+Most source files are licensed under the terms of the <cite>Mozilla
+  Public License, version 2.0</cite>.
+
+[REUSE]: <https://reuse.software/spec/>
+[draft-phillips-record-jar-01]: <https://datatracker.ietf.org/doc/html/draft-phillips-record-jar-01>
+[rdar-92753335]: <https://github.com/apple-oss-distributions/patch_cmds/blob/5084833f90df1b0e0924ea56f94c0199b3b8bbc6/diff/diffreg.c#L1800-L1808>