Improve build command with Gemini support

sbs can now convert gemtext to markdown which allows mixing gemini and
markdown in the same site directory and easy publishing of gemini
content for the web.

A modification of the build command was also added to allow building the
entire site without specifying any paths.

sbs

@@ -139,7 +139,7 @@ build()
 {
 	for file in "$@"; do
 		if [ -d "$file" ]; then
-			"$0" build "$file"/*
+			build "$file"/*
 			continue
 		elif [ ! -f "$file" ]; then
 			printf "ERROR: %s does not exist.\n" "$file"
@@ -150,18 +150,34 @@ build()
 		subDir=$(dirname "$file" | sed "s/^content//")
 		mkdir -p "static/$subDir"
 
+		# Convert Gemtext files to Markdown
+		# The first sed expression converts all local links that end
+		# in .gmi to .html (e.g. /blog/post1.gmi --> /blog/post1.html).
+		# The second sed expression converts all gemini-style links to
+		# markdown-style links.
+		if [ "$(echo "$file" | awk -F\. '{print $NF}' )" = "gmi" ]; then
+			printf "Converting: %s to markdown...\n" "$file"
+			fileName=$(basename "$file" .gmi)
+			sed -e 's/\(=> \/\)\(.*\)\(.gmi\)\(.*\)/\1\2.html\4/g' \
+				-e 's/=> \([^ ]*\) \(.*\)/[\2](\1)\n/g' \
+				"$file" > /tmp/sbs/"$fileName".md
+			title=$(grep '^# ' "$file" | head -n1 | cut -d' ' -f2-)
+			description="Page auto-converted from the Gemini format."
+			file=/tmp/sbs/"$fileName".md
+		fi
+
 		printf "Creating: static%s/%s.html...\n" "$subDir" "$fileName"
 
-		# Extract metadata from the markdown document
-		title=$(lowdown -X title "$file")
-		meta=$(lowdown -X summary "$file")
+		# Extract metadata from markdown doc (if not converted from gmi)
+		title=${title:-$(lowdown -X title "$file")}
+		description=${description:-$(lowdown -X summary "$file")}
 
 		# Build and process the output document
 		lowdown $buildOptions "$file" \
 			| cat "templates/header.html" - "templates/footer.html" \
 			| sed -e "s/<title><\/title>/<title>$title - $siteName<\/title>/" \
 			-e "s/lang=\"\"/lang=\"$languageCode\"/" \
-			-e "s/content=\"\"/content=\"$meta\"/" \
+			-e "s/content=\"\"/content=\"$description\"/" \
 			> "static/$subDir/$fileName".html
 
 		printf "Created: static%s/%s.html\n" "$subDir" "$fileName"
@@ -179,7 +195,14 @@ case "$1" in
 	"build")
 		shift
 		parse_configuration
-		build "$@"
+		mkdir -p /tmp/sbs/
+		# Allows simply running "sbs build" without path(s)
+		if [ $# -eq 0 ]; then
+			build ./content/*
+		else
+			build "$@"
+		fi
+		rm -rf /tmp/sbs/
 		;;
 	"genfeed")
 		parse_configuration