Improve global params in parsers/transforms

[Shushe] / README.markdown

diff --git a/README.markdown b/README.markdown
index 7e9b74bc2069b41b83e97dd8d54512b2364febeb..400679f090097a8bbb2368fc438a55c6a5c57084 100644 (file)
--- a/README.markdown
+++ b/README.markdown
@@ -98,6 +98,7 @@ In every case, you may supply your own implementation by overriding the
 - `echo`
 - `file`
 - `find`
+- `git` (optional; set `GIT=` to disable)
 - `mkdir` (requires support for `-p`)
 - `mv`
 - `od` (requires support for `-t x1`)
@@ -160,7 +161,8 @@ The following additional variables can be used to control the behaviour
 - **`FINDRULES`:**
   Rules to use with `find` when searching for source files.
   The default ignores hidden files, those that start with a period or
-    hyphen‐minus, and those which contain a pipe, buck, or colon.
+    hyphen‐minus, and those which contain a pipe, buck, percent, or
+    colon.
 
 - **`FINDINCLUDERULES`:**
   Rules to use with `find` when searching for includes (default:
@@ -254,8 +256,10 @@ For example, the trivial `text/plain` parser is defined as follows :⁠—
 <transform
   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"
 >
+  <书社:id>example:text/plain</书社:id>
   <template match="html:script[@type='text/plain']">
     <html:pre><value-of select="."/></html:pre>
   </template>
@@ -270,8 +274,21 @@ Alternatively, you can set the `@书社:supported-media-types` attribute
   on the root element of the parser to override media type support
   detection.
 
-Parsers can also target specific dialects of X·M·L, in which case they
-  operate on the same basic principles as transforms (described below).
+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
@@ -304,6 +321,15 @@ 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,
@@ -349,10 +375,32 @@ The following are recommendations on effective creation of
 - Set `@exclude-result-prefixes` on the root `xslt:transform` element
     to reduce the number of declared namespaces in the final result.
 
-The params `$buildtime`, `$srctime`, and `$path` are available within
-  transforms and are initialized to the current time, the time that the
-  source file was last modified, and the path of the output file within
-  $(DESTDIR).
+## Global Params
+
+The following params are made available globally in parsers and
+  transforms :⁠—
+
+- **`BUILDTIME`:**
+  The current time.
+
+- **`SRCREV`:**
+  The tag or hash of the current commit in the working directory (if
+    `GIT` is defined and `./.git` exists).
+
+- **`SRCTIME`:**
+  The time at which the source file was last modified.
+
+- **`VERSION`:**
+  The tag or hash of the current commit in `THISDIR` (if `GIT` is
+    defined and `$(THISDIR)/.git` exists).
+
+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