Re-wrote from scratch in Golang

- Re-implemented the project in Golang, and deprecated Python entirely
- Implemented several new, long-requested features
- Refactored cheatsheets into a separate repository

internal/sheets/filter.go

@@ -0,0 +1,53 @@
+package sheets
+
+import (
+	"strings"
+
+	"github.com/cheat/cheat/internal/sheet"
+)
+
+// Filter filters cheatsheets that do not match `tag(s)`
+func Filter(
+	cheatpaths []map[string]sheet.Sheet,
+	tags []string,
+) []map[string]sheet.Sheet {
+
+	// buffer a map of filtered cheatsheets
+	filtered := make([]map[string]sheet.Sheet, 0, len(cheatpaths))
+
+	// iterate over each cheatpath
+	for _, cheatsheets := range cheatpaths {
+
+		// create a map of cheatsheets for each cheatpath. The filtering will be
+		// applied to each cheatpath individually.
+		pathFiltered := make(map[string]sheet.Sheet)
+
+		// iterate over each cheatsheet that exists on each cheatpath
+		for title, sheet := range cheatsheets {
+
+			// assume that the sheet should be kept (ie, should not be filtered)
+			keep := true
+
+			// iterate over each tag. If the sheet does not match *all* tags, filter
+			// it out.
+			for _, tag := range tags {
+				if !sheet.Tagged(strings.TrimSpace(tag)) {
+					keep = false
+				}
+			}
+
+			// if the sheet does match all tags, it passes the filter
+			if keep {
+				pathFiltered[title] = sheet
+			}
+		}
+
+		// the sheets on this individual cheatpath have now been filtered. Now,
+		// store those alongside the sheets on the other cheatpaths that also made
+		// it passed the filter.
+		filtered = append(filtered, pathFiltered)
+	}
+
+	// return the filtered cheatsheets on all paths
+	return filtered
+}