merge together similar copyright statements

Author: pietroalbini

src/tools/collect-license-metadata/src/licenses.rs

@@ -1,5 +1,7 @@
 use std::collections::HashMap;
 
+const COPYRIGHT_PREFIXES: &[&str] = &["SPDX-FileCopyrightText:", "Copyright", "(c)", "(C)", "©"];
+
 pub(crate) struct LicensesInterner {
     by_id: Vec<License>,
     by_struct: HashMap<License, usize>,
@@ -10,7 +12,8 @@ impl LicensesInterner {
         LicensesInterner { by_id: Vec::new(), by_struct: HashMap::new() }
     }
 
-    pub(crate) fn intern(&mut self, license: License) -> LicenseId {
+    pub(crate) fn intern(&mut self, mut license: License) -> LicenseId {
+        license.simplify();
         if let Some(id) = self.by_struct.get(&license) {
             LicenseId(*id)
         } else {
@@ -35,3 +38,28 @@ pub(crate) struct License {
     pub(crate) spdx: String,
     pub(crate) copyright: Vec<String>,
 }
+
+impl License {
+    fn simplify(&mut self) {
+        self.remove_copyright_prefixes();
+        self.copyright.sort();
+        self.copyright.dedup();
+    }
+
+    fn remove_copyright_prefixes(&mut self) {
+        for copyright in &mut self.copyright {
+            let mut stripped = copyright.trim();
+            let mut previous_stripped;
+            loop {
+                previous_stripped = stripped;
+                for pattern in COPYRIGHT_PREFIXES {
+                    stripped = stripped.trim_start_matches(pattern).trim_start();
+                }
+                if stripped == previous_stripped {
+                    break;
+                }
+            }
+            *copyright = stripped.into();
+        }
+    }
+}