largefiles: introduce "_lfcommithooks" to abstract pre-committing procedures
This changes allows to customize pre-committing procedures according
to conditions.
This patch uses "stack" with an element instead of flag like
"_isXXXXing" or so, because:
- the former works correctly even when customizations are nested, and
- ensuring at least one element can ignore empty check
basic:
* neither file exists
creating
* neither file still exists
* empty file x created
creating
* file x changed size
creating
* nothing changed with either file
* file x changed inode
creating
* empty file y created
creating
* file y changed size
creating
* file y changed inode
creating
* both files changed inode
creating
fakeuncacheable:
* neither file exists
creating
* neither file still exists
creating
* empty file x created
creating
* file x changed size
creating
* nothing changed with either file
creating
* file x changed inode
creating
* empty file y created
creating
* file y changed size
creating
* file y changed inode
creating
* both files changed inode
creating
repository tip rolled back to revision -1 (undo commit)
working directory now based on revision -1
repository tip rolled back to revision -1 (undo commit)
working directory now based on revision -1
setbeforeget:
* neither file exists
string set externally
* file x created
creating
string from function
* string set externally again
string 2 set externally
* file y created
creating
string from function