Added documentation for wildcards and indentation rules

Author: alberti42

docs/manual.md

@@ -108,6 +108,8 @@ For clarity: the three available prefixes `/!` and `/!!` and `/!!!` allow for fu
 
 Currently, the below simple wildcard syntax is supported for sorting group:
 
+For practical notes and examples (including common `...` gotchas and indentation), see [wildcards.md](./wildcards.md).
+
 ### A single digit (exactly one)
 
 An expression like `\d` or `\[0-9]` matches a single digit (exactly one)

docs/syntax-reference.md

@@ -32,6 +32,7 @@ The intention is to make it understandable to non-technical persons.
   - the YAML key `sorting-spec:` has to be used
   - because indentation matters, the recommended multiline YAML syntax is `sorting-spec: |`
     - refer to YAML syntax reference for details on how the pipe `|` character works (e.g. https://en.wikipedia.org/wiki/YAML#Basic_components)
+    - for practical notes and examples about `...` and indentation, see [wildcards.md](./wildcards.md)
 - the `sorting specification` comprises one or more [sections](#Section)
   - each `section` has to reside in a single location (a single entry in frontmatter YAML of a note)
   - multiple `sections` can exist under a single `sorting-spec: |` YAML entry, one after another

docs/wildcards.md

@@ -0,0 +1,124 @@
+# Wildcards and Pattern Matching
+
+This plugin stores its configuration in YAML frontmatter. The value of
+`sorting-spec: |` is a multi-line string containing the plugin's sorting
+specification "language" (the plugin docs call it an informal language / syntax).
+
+In this document we may refer to it as a DSL (Domain-Specific Language): a small
+purpose-built language parsed by the plugin.
+
+In examples below, snippets may show only the sorting-spec lines (the content
+that goes under `sorting-spec: |`) for brevity.
+
+Some parts of the syntax look regex-like (for example `\d\d\d\d`), but matching
+is not "full regex everywhere". In particular, the `...` token is a plugin
+wildcard and should not be treated as the regex `.*`.
+
+## The `...` wildcard
+
+`...` is used for prefix/suffix matching and for patterns where you want to
+match an arbitrary run of characters.
+
+Examples:
+
+- `Focus...` matches names starting with `Focus`.
+- `...ive` matches names ending with `ive`.
+- `A...s` matches names starting with `A` and ending with `s`.
+
+Practical rules:
+
+- Any characters you place next to `...` (including spaces) are literal and must
+  exist in the name.
+- If you want to match an exact name shape that ends where your pattern ends,
+  omit `...`.
+
+### Example: year folders
+
+Given folders:
+
+- `Reviewed in 2023`
+- `Reviewed in 2024`
+- `Reviewed in 2025`
+- `Reviewed in 2026`
+
+To match them exactly as a group, prefer:
+
+```yaml
+/folders Reviewed in 20\d\d
+ > a-z
+```
+
+If you write:
+
+```yaml
+/folders Reviewed in 20\d\d ...
+ > a-z
+```
+
+note the space before `...`. That space is a literal character, so this pattern
+only matches names that contain a space after the year (for example `Reviewed in
+2026 Q1`), and it will _not_ match exact names like `Reviewed in 2026`.
+
+If you want to allow an optional suffix that starts with a space, but also match
+the exact name, define two groups (exact first), or use an exact match without
+`...`.
+
+## Digits and ISO dates
+
+Common digit patterns:
+
+- `\d` matches one digit.
+- `\d\d\d\d` is often used for years.
+
+ISO date prefixes (`YYYY-MM-DD`) sort correctly as plain text, so reverse
+alphabetical (`> a-z`) gives newest-first:
+
+```yaml
+/:files \d\d\d\d-\d\d-\d\d ...
+ > a-z
+```
+
+## Indentation matters
+
+In the plugin docs, the lines like `< a-z`, `> a-z`, `< modified` are referred to
+as sorting instructions / sorting methods (not a YAML concept). In this file we
+use the term "sorting instruction".
+
+A sorting instruction must be indented under the group it applies to.
+
+More precisely: inside the `sorting-spec: |` text, the sorting instruction line
+must start at a greater indentation level than the group line immediately above
+it (at least one extra space).
+
+```yaml
+/folders Reviewed in 20\d\d
+  > a-z
+```
+
+In contrast, this is *not* grouped correctly (same indentation as the group
+line):
+
+```yaml
+/folders Reviewed in 20\d\d
+> a-z
+```
+
+If the sorting instruction is not indented more than the group line, the plugin
+will not associate it with that group.
+
+## Complete example (folders first, then files)
+
+Full YAML frontmatter form:
+
+```yaml
+---
+sorting-spec: |
+  target-folder: 03 Literature review
+  /folders Reviewed in 20\d\d
+   > a-z
+  /folders
+   < a-z
+  /:files
+   < a-z
+---
+```