Improve make format.

 * Use `yapf` from environment if it exists.
 * Better way to generate exclude.

Signed-off-by: Tim 'mithro' Ansell <me@mith.ro>

Makefile

@@ -2,6 +2,7 @@ CLANG_FORMAT ?= clang-format-5.0
 
 .PHONY: database format clean env
 
+IN_ENV = if [ -e env/bin/activate ]; then . env/bin/activate; fi;
 env:
 	virtualenv --python=python3 env
 	. env/bin/activate; pip install -r requirements.txt
@@ -15,11 +16,13 @@ build:
 database: build
 	$(MAKE) -C $@
 
+FORMAT_EXCLUDE = third_party git env build
+FIND_EXCLUDE = $(foreach x,$(FORMAT_EXCLUDE),-and -not -path './$(x)/*')
 format:
-	find . -name \*.cc -and -not -path './third_party/*' -and -not -path './.git/*' -exec $(CLANG_FORMAT) -style=file -i {} \;
-	find . -name \*.h -and -not -path './third_party/*' -and -not -path './.git/*' -exec $(CLANG_FORMAT) -style=file -i {} \;
-	find . -name \*.py -and -not -path './third_party/*' -and -not -path './.git/*' -exec yapf -p -i {} \;
-	find . -name \*.tcl -and -not -path './third_party/*' -and -not -path './.git/*' -exec ${XRAY_TCL_REFORMAT} {} \; 2>/dev/null
+	find . -name \*.cc $(FIND_EXCLUDE) -exec $(CLANG_FORMAT) -style=file -i {} \;
+	find . -name \*.h $(FIND_EXCLUDE) -exec $(CLANG_FORMAT) -style=file -i {} \;
+	$(IN_ENV) find . -name \*.py $(FIND_EXCLUDE) -exec yapf -p -i {} \;
+	find . -name \*.tcl $(FIND_EXCLUDE) -exec ${XRAY_TCL_REFORMAT} {} \; 2>/dev/null
 
 clean:
 	$(MAKE) -C database clean