sqlite 3 view: use 'immutable=1' URI parameter to prevent leaving wal/shm files after viewing sqlite database

[karlicoss]

The problem I often had with viewing .sqlite files with mc is that exiting the view mode mid-way may leave .wal/.shm files in the database directory.
This never caused any actual issues, but a bit annoying, since leftover .wal files are often a sign that the program working with the database exited ungracefully.
This effectively reproduces mc's behaviour:

/tmp/testsqlite $ rm -f *-wal *-shm && sqlite3 "/tmp/testsqlite/db file.sqlite" .dump | head >/dev/null && ls -1 /tmp/testsqlite/
'db file.sqlite'
'db file.sqlite-shm'
'db file.sqlite-wal'

After the change -- no shm/wal files:

/tmp/testsqlite $ rm -f *-wal *-shm && sqlite3 "file:/tmp/testsqlite/db file.sqlite?immutable=1" .dump | head >/dev/null && ls -1 /tmp/testsqlite/
'db file.sqlite'

You can find the docs on immutable mode here ​https://www.sqlite.org/uri.html#uriimmutable
Immutable mode has been supported in sqlite since 2014: ​https://www.sqlite.org/changes.html#version_3_8_5
In case user's sqlite installation is older, the mode is just quietly ignored, so the change is backwards compatible.

[karlicoss]

One downside of this change I know of is that now if you're trying to view a database with an uncommitted WAL,the WAL is basically ignored, whereas previously it would also display the changes in WAL.

This may or may not be desirable (personally I'd rather prefer for it not to dump empty WAL files). If we want to preserve the old behaviour, could change the viewer to be adaptive: if there are no existing -wal files, use immutable mode; otherwise open in the default mode which would also display uncommitted changes.

[karlicoss]

also in the meantime, if you want to achieve that behaviour, you can use this in your local ext config (~/.config/mc/mc.ext)

# sqlite3.db
type/^SQLite 3.x database
	Open=/usr/lib/mc/ext.d/misc.sh open sqlite
	View=%view{ascii} sqlite3 file:%f?immutable=1 .dump

[andrew_b]

Thanks.
Applied as [ebbdc8847ecfedb587d494a6b85a76ec8f1c9e8b].