Changes the sat switch so it can be disabled (#1219)

src/nimblepkg/options.nim

@@ -550,7 +550,13 @@ proc parseFlag*(flag, val: string, result: var Options, kind = cmdLongOption) =
  result.developFile = val.normalizedPath
  else:
  raise nimbleError(multipleDevelopFileOptionsGivenMsg)
- of "sat": result.useSatSolver = true 
+ of "solver": 
+ if val == "sat":
+ result.useSatSolver = true
+ elif val == "legacy":
+ result.useSatSolver = false
+ else:
+ raise nimbleError("Unknown solver option: " & val)
  else: isGlobalFlag = false
 
  var wasFlagHandled = true

tests/tsat.nim

@@ -150,7 +150,7 @@ suite "SAT solver":
  where c has two versions of the same package. The version is retrieved counterintuitively from 
  the nimblemeta.json special version field. 
  ]#
- let (_, exitCode) = execNimble("install", "-l", "--sat")
+ let (_, exitCode) = execNimble("install", "-l", "--solver:sat")
  check exitCode == QuitSuccess
 
  test "should be able to download a package and select its deps":