make: create a new file

- Creates a templates and a notes directory.
- Creates a default template used to create new files. It contains a
  minimal frontmatter with the creation date and an ID.
- Adds the *new* recipe which creates a new file in the notes directory,
  based on the default template, replacing the creation date and ID
  variables with according values.
- Updates the README file with the new recipe.
- Improves the documentation of the code with comments.
- Fixes #9.

Co-Authored-by: iGor milhit <igor@milhit.ch>

Makefile

@@ -6,10 +6,27 @@
 .DEFAULT_GOAL:=help
 SHELL:=/bin/bash
 
+# Get the output of the pandoc command
 pandoc=$(shell command -v pandoc)
+# Get the version of pandoc
 pandoc_version=$(shell pandoc --version | sed -e 's/.* // ; 1q')
+# Get the output of the awk command
 awk=$(shell command -v awk)
 
+# Get the datetime
+now=$(shell date +%Y%m%d%H%M%S)
+# Build the filename
+filename=$(now).md
+
+# Export date and id as environment variable to replace the variables in the
+# template file
+export date:=$(shell date +%Y-%m-%dT%H:%M:%S%:z)
+export id:=$(now)
+
+# Set the templates and notes directories
+templates_directory=templates
+notes_directory=notes
+
 .PHONY: help deps
 
 help:  ## Display this help
@@ -18,12 +35,17 @@ help:  ## Display this help
 deps:  ## Check dependencies
 	$(info Checking and getting dependencies)
 ifeq ($(strip ($pandoc)),)
-	@echo "pandoc is required"
+	@echo "pandoc is required and not installed"
 else
 	@echo "pandoc" $(pandoc_version) "is installed"
 endif
 ifeq ($(strip ($awk)),)
-	@echo "awk is required"
+	@echo "awk is required and not installed"
 else
 	@echo "awk is installed"
 endif
+
+new: ## Create a new file
+	$(info Creating a new file)
+	@ envsubst <$(templates_directory)/default.md >$(notes_directory)/$(filename)
+	$(info Your new file is $(notes_directory)/$(filename))

templates/default.md

@@ -0,0 +1,6 @@
+---
+date: $date
+id: $id
+---
+
+