apk: add --purge option (fixes #61)

and do not remove modified configuration files unless --purge is
specified.

src/apk.c

@@ -43,6 +43,8 @@ static struct apk_option generic_options[] = {
 	{ 0x101, "progress",	"Show a progress bar" },
 	{ 0x102, "clean-protected", "Do not create .apk-new files to "
 				"configuration dirs" },
+	{ 0x106, "purge",	"Delete also modified configuration files on "
+				"package removal" },
 	{ 0x103, "allow-untrusted", "Blindly install packages with untrusted "
 				"signatures or no signature at all" },
 	{ 0x104, "simulate",	"Show what would be done without actually "
@@ -359,6 +361,9 @@ int main(int argc, char **argv)
 		case 0x104:
 			apk_flags |= APK_SIMULATE;
 			break;
+		case 0x106:
+			apk_flags |= APK_PURGE;
+			break;
 		case 0x105:
 			apk_wait = atoi(optarg);
 			break;

src/apk_defines.h

@@ -60,6 +60,7 @@ extern unsigned int apk_flags;
 #define APK_PREFER_AVAILABLE	0x0040
 #define APK_UPDATE_CACHE	0x0080
 #define APK_ALLOW_UNTRUSTED	0x0100
+#define APK_PURGE		0x0200
 
 #define apk_error(args...)	do { apk_log("ERROR: ", args); } while (0)
 #define apk_warning(args...)	do { if (apk_verbosity > 0) { apk_log("WARNING: ", args); } } while (0)

src/database.c

@@ -1425,6 +1425,7 @@ static void apk_db_purge_pkg(struct apk_database *db, struct apk_package *pkg,
 	struct apk_db_dir_instance *diri;
 	struct apk_db_file *file;
 	struct apk_db_file_hash_key key;
+	struct apk_file_info fi;
 	struct hlist_node *dc, *dn, *fc, *fn;
 	unsigned long hash;
 	char name[1024];
@@ -1439,7 +1440,11 @@ static void apk_db_purge_pkg(struct apk_database *db, struct apk_package *pkg,
 				.filename = APK_BLOB_PTR_LEN(file->name, file->namelen),
 			};
 			hash = apk_blob_hash_seed(key.filename, diri->dir->hash);
-			unlink(name);
+			if (!(diri->dir->flags & APK_DBDIRF_PROTECTED) ||
+			    (apk_flags & APK_PURGE) ||
+			    (apk_file_get_info(name, file->csum.type, &fi) == 0 &&
+			     apk_checksum_compare(&file->csum, &fi.csum) == 0))
+				unlink(name);
 			if (apk_verbosity > 1)
 				printf("%s\n", name);
 			__hlist_del(fc, &diri->owned_files.first);