New ncdu, ncdc + btrfssize + misc changes

dat/ncdu-man

@@ -103,6 +103,11 @@ List sizes using base 10 prefixes, that is, powers of 1000 (KB, MB, etc), as
 defined in the International System of Units (SI), instead of the usual base 2
 prefixes, that is, powers of 1024 (KiB, MiB, etc).
 
+=item --confirm-quit
+
+Requires a confirmation before quitting ncdu. Very helpful when you
+accidentally press 'q' during or after a very long scan.
+
 =back
 
 =head2 Scan Options
@@ -214,9 +219,14 @@ Refresh/recalculate the current directory.
 
 Spawn shell in current directory.
 
-We first check the $SHELL environment variable of the user for the preferred
-shell interpreter. If it's not set, we fall back to the compile time
-configured default shell (usually /bin/bash).
+Ncdu will determine your preferred shell from the C<NCDU_SHELL> or C<SHELL>
+variable (in that order), or will call C</bin/sh> if neither are set.  This
+allows you to also configure another command to be run when he 'b' key is
+pressed. For example, to spawn the L<vifm(1)> file manager instead of a shell,
+run ncdu as follows:
+
+  export NCDU_SHELL=vifm
+  ncdu
 
 =item q
 
@@ -307,7 +317,12 @@ or multicolumn characters.
 
 All sizes are internally represented as a signed 64bit integer. If you have a
 directory larger than 8 EiB minus one byte, ncdu will clip its size to 8 EiB
-minus one byte.
+minus one byte. When deleting items in a directory with a clipped size, the
+resulting sizes will be incorrect.
+
+Item counts are stored in a signed 32-bit integer without overflow detection.
+If you have a directory with more than 2 billion files, quite literally
+anything can happen.
 
 Please report any other bugs you may find at the bug tracker, which can be
 found on the web site at https://dev.yorhel.nl/ncdu