docs: add "make docs" target to wrap Doxygen

.gitignore

@@ -1,3 +1,6 @@
+# Doxygen output from "make docs"
+docs/
+
 *.sqlite
 
 # Byte-compiled / optimized / DLL files

Doxyfile

@@ -58,7 +58,7 @@ PROJECT_LOGO           =
 # entered, it will be relative to the location where doxygen was started. If
 # left blank the current directory will be used.
 
-OUTPUT_DIRECTORY       =
+OUTPUT_DIRECTORY       = docs
 
 # If the CREATE_SUBDIRS tag is set to YES then doxygen will create 4096 sub-
 # directories (in 2 levels) under the output directory of each output format and
@@ -1817,7 +1817,7 @@ EXTRA_SEARCH_MAPPINGS  =
 # If the GENERATE_LATEX tag is set to YES, doxygen will generate LaTeX output.
 # The default value is: YES.
 
-GENERATE_LATEX         = YES
+GENERATE_LATEX         = NO
 
 # The LATEX_OUTPUT tag is used to specify where the LaTeX docs will be put. If a
 # relative path is entered the value of OUTPUT_DIRECTORY will be put in front of

Makefile

@@ -189,6 +189,14 @@ help: ## Print this message and exit.
 version:
 	@python -c "import securedrop_client; print(securedrop_client.__version__)"
 
+
+.PHONY: docs
+docs:  ## Generate browsable documentation and call/caller graphs (requires Doxygen and Graphviz)
+	@which doxygen >> /dev/null || { echo "doxygen(1) is not available in your \$$PATH.  Is it installed?"; exit 1; }
+	@which dot >> /dev/null || { echo "Graphviz's dot(1) is not available in your \$$PATH.  Is it installed?"; exit 1; }
+	@doxygen
+	@echo "Now open \"$(PWD)/docs/html/index.html\" in your browser."
+
 ##############
 #
 # Localization