remove depth from Savepoint

[Taywee]

Savepoints with the same name nest properly without issue. This doesn't work with rusqlite unless savepoints are always released on drop.

closes #1326

[codecov]

Codecov Report

Patch coverage: 96.00% and project coverage change: +0.26 🎉

Comparison is base (65e4be3) 80.48% compared to head (8545c5d) 80.75%.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1327      +/-   ##
==========================================
+ Coverage   80.48%   80.75%   +0.26%     
==========================================
  Files          49       49              
  Lines        9950    10094     +144     
==========================================
+ Hits         8008     8151     +143     
- Misses       1942     1943       +1     

Impacted Files	Coverage Δ
src/transaction.rs	95.80% <96.00%> (+2.11%)	⬆️

... and 10 files with indirect coverage changes

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[gwenn]

I guess that:

rusqlite/src/transaction.rs

Line 347 in 841014b

DropBehavior::Commit => self.commit_().or_else(|_| self.rollback()),

is buggy.
In case of error on RELEASE, we ROLLBACK the savepoint.
But we should ROLLBACK AND RELEASE, no?

sqlite> PRAGMA foreign_keys = true;
sqlite> CREATE TABLE r(n INTEGER PRIMARY KEY NOT NULL);
sqlite> CREATE TABLE f(n REFERENCES r(n) DEFERRABLE INITIALLY DEFERRED);
sqlite> SAVEPOINT s;
sqlite> INSERT INTO f VALUES (0);
sqlite> RELEASE s;
Runtime error: FOREIGN KEY constraint failed (19)
sqlite> ROLLBACK TO s;
sqlite> COMMIT; -- does not fail because s is still on the stack...
sqlite>

[Taywee]

Ah, yes, you're right. I had overlooked that.