Update changelog and installation instructions

CHANGELOG.md

@@ -13,6 +13,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
   MacOS and Windows for packages from <https://pypi.org/project/pineappl/>
 - added support for scale uncertainties calculated with the covariance method,
   and for combined PDF and scale uncertainties
+- added support for installing man pages. See installation instructions for
+  more information
 
 ### Changed
 
@@ -22,6 +24,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - `pineappl pdfunc` was renamed into `pineappl uncert`, which is now also able
   to calculate scale uncertainties, which in turn have been removed from
   `pineappl convolute`
+- `pineappl help` now relies on installed man pages
 
 ### Fixed
 

docs/installation.md

@@ -148,6 +148,13 @@ this repository and run
 
 inside it.
 
+### Man pages
+
+Man pages for the CLI can be installed from a repository with
+
+    mkdir -p $(dirname $(which pineappl))/../share/man/man1/
+    cargo xtask install-manpages $(dirname $(which pineappl))/../share/man/man1/
+
 ## Python
 
 [![PyPI version](https://badge.fury.io/py/pineappl.svg)](https://badge.fury.io/py/pineappl)