-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`).