[#1455] CONTRIBUTING.md: automatic formatting

diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index 7b88aee169e1fca9c8400d204df770f3a1bb7050..0178cc671e05f54b55db6a28a626fae55035097d 100644 (file)
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -42,6 +42,8 @@ expected to run on many other architectures. You may take a look at [system spec
 notes](https://kb.isc.org/docs/installing-kea). For a complete list of systems we build on, you may
 take a look at the [Jenkins build farm](https://jenkins.isc.org/).
 
+### Coding guidelines
+
 Does your patch conform to [Kea coding
 guidelines](https://gitlab.isc.org/isc-projects/kea/wikis/coding-guidelines)?  You can submit a
 patch that does not adhere to them, but that will reduce its chances of being accepted.  If the
@@ -49,6 +51,39 @@ deviations are minor, one of the Kea engineers who does the review will likely f
 However, if there are lots of issues, the reviewer may simply reject the patch and ask you to fix it
 before re-submitting.
 
+Placed in the root of the repository are files that formally describe the coding
+guidelines above as close as possible. They are `.clang-format` and
+`.uncrustify.cfg` used by `clang-format` and `uncrustify` respectively. If you
+want to format code automatically, you will need to have at least one of these
+tools installed. Since by default, these tools look for the closest style file
+located in one of the parent directories or, otherwise, in a default location,
+there are a a couple of helpful scripts i.e. `./tools/clang-format.sh` and
+`./tools/uncrustify.sh` to assure you that the Kea-owned file is used. They
+accept any number of customized parameters that would be passed to the
+underlying tool followed by any number of files and/or directories. Passing
+directories will have all non-generated C++ files under it formatted.
+
+IDEs often offer support for code formatting tools. For example, in Visual
+Studio Code, you may install `Clang-Format` and `crustless` through the Command
+Palette (`Ctrl + Shift + P` by default), `Extensions: Install Extensions`.
+Then open a source file, select code that you want formatted, open the Command
+Palette, and choose `Format Selection`. You might go through an onboarding step
+where you choose the formatter in the case you have both installed, but that
+should be it.
+
+When using these tools, it can be tempting to format entire files at once. In
+the interest of preserving git history as much as possible, it is recommended
+that you only format code that you have added or changed. This is much easier
+done in an IDE, but as long as the tool supports it, it can be done using the
+provided scripts e.g.:
+
+```bash
+./tools/clang-format.sh --lines=13:37 ./src/lib/dhcpsrv/alloc_engine.cc
+```
+
+Uncrustify does not seem to have a line-range-limiting option at the time of
+this writing.
+
 ## Running unit-tests
 
 One of the ground rules in Kea development is that every piece of code has to be tested. We now have