cmake: Update coding style to use lowercase commands

Also updates our coding style file.

Ancient CMake versions required upper-case commands.  Later command
names became case-insensitive.  Now the preferred style is lower-case.

Run the following shell code (with GNU compliant sed):

cmake --help-command-list | grep -v "cmake version" | while read c; do
  echo 's/\b'"$(echo $c | tr '[:lower:]' '[:upper:]')"'\(\s*\)(/'"$c"'\1(/g'
done > convert.sed \
&& git ls-files -z -- bootstrap '*.cmake' '*.cmake.in' \
'*CMakeLists.txt' | xargs -0 gsed -i -f convert.sed && rm convert.sed

(Make sure the backslashes don't get mangled!)

1 files changed, 3 insertions, 0 deletions

diff --git a/CODING.md b/CODING.md
index 7b2dda931..d84d062de 100644
--- a/CODING.md
+++ b/CODING.md
@@ -125,6 +125,9 @@ std::map<std::string, std::string> bar =
 * Pylint is good tool for helping with following code guidelines. It's very
   fussy though, so don't get too worked up about following its suggestions.
 
+## CMake-specific Guidelines
+
+* CMake commands written in lowercase.
 
 ## Revision Control Hygiene