Remove per-operation Open()/Close() calls to BoltDB

[js-ojus]

• Context now maintains a DB handle that is kept alive

[odeke-em]

We'll need to handle at least OpenDB() errors, please set it to

exitWithError(context.OpenDB())

[odeke-em]

I've added a few comments.
Also please do this for indexCmd

--git a/cmd/drive/main.go b/cmd/drive/main.go
index b417f20..f43d837 100644
--- a/cmd/drive/main.go
+++ b/cmd/drive/main.go
@@ -411,6 +411,9 @@ func (cmd *indexCmd) Run(args []string) {
    byMatches := *cmd.matches
    sources, context, path := preprocessArgsByToggle(args, byMatches || byId)

+   exitWithError(context.OpenDB())
+   defer context.CloseDB()
+
    options := &drive.Options{
        Sources:           sources,
        Hidden:            *cmd.hidden,

[js-ojus]

I have made the suggested changes @odeke-em! Please take a look at it again.

[odeke-em]

if c.DB == nil {
    return errors.New("nil dereference of db")
}
return c.DB.Close()

[odeke-em]

Thanks @js-ojus, just one more and then we are good to go.

[odeke-em]

Once that is in, please help me squash the commits into one and then I'll merge it in.
Thank you again.

[js-ojus]

Hello @odeke-em! I have squashed the commits into a single one, which is now reflected in the pull request.

[odeke-em]

LGTM! Thank you very much for diagnosing, and working on this.