cabal install FILE fails when path doesn't start with a letter

[typedrat]

$ install_from_tarball
Reading available packages of hackage.haskell.org...
Using most recent state specified from most recent cabal update
index-state(hackage.haskell.org) = 2018-12-31T19:00:57Z
CallStack (from HasCallStack):
  die', called at ./Distribution/Client/TargetSelector.hs:701:9 in main:Distribution.Client.TargetSelector
cabal: Unrecognised target '../dist-newstyle/sdist/Cabal-2.5.0.0.tar.gz'.
Expected a meta-target 'all' or component kind filter or component name or
package name or package directory or package .cabal file or component name or
module name or file, rather than
'../dist-newstyle/sdist/Cabal-2.5.0.0.tar.gz'.

Discovered bugsquashing for #5800.

[typedrat]

$ install_from_tarball
Reading available packages of hackage.haskell.org...
Using most recent state specified from most recent cabal update
index-state(hackage.haskell.org) = 2018-12-31T20:27:18Z
CallStack (from HasCallStack):
  die', called at ./Distribution/Client/TargetSelector.hs:701:9 in main:Distribution.Client.TargetSelector
cabal: Unrecognised target
'/home/travis/build/haskell/cabal/dist-newstyle/sdist/Cabal-2.5.0.0.tar.gz'.
Expected a meta-target 'all' or component kind filter or component name or
package name or package directory or package .cabal file or component name or
module name or file, rather than
'/home/travis/build/haskell/cabal/dist-newstyle/sdist/Cabal-2.5.0.0.tar.gz'.

This is... pretty bad.

[typedrat]

Honestly not sure how to fix this. Should we change how file targets work, or just add a filter that checks for tarball arguments before we even go down that road?

[jneira]

I've got other errors in windows with cabal-install-3.4.0.0

PS D:\dev\ws\haskell\cabal-test\tmp> cabal install ..\dist-newstyle\sdist\cabal-test-0.1.0.0.tar.gz
cabal-3.4.0.0.exe: Invalid package ID:
..\dist-newstyle\sdist\cabal-test-0.1.0.0.tar.gz
"<eitherParsec>" (line 1, column 3):
unexpected all digits or a dot in a portion of package name
expecting "-"

PS D:\dev\ws\haskell\cabal-test\tmp> cd ..
PS D:\dev\ws\haskell\cabal-test> cabal install dist-newstyle\sdist\cabal-test-0.1.0.0.tar.gz
cabal-3.4.0.0.exe: Unknown target
'dist-newstyle\sdist\cabal-test-0.1.0.0.tar.gz'.
The package cabal-test has no file target
'dist-newstyle\sdist\cabal-test-0.1.0.0.tar.gz'.