Unable to understand "Different databases" section in stack document - haskell

Question

I' reading stack document from https://docs.haskellstack.org/en/stable/GUIDE/
In the section of Different databases, it says that
Databases in stack are layered. For example, the database listing we just gave is called a local database. That is layered on top of a snapshot database, which contains the libraries and executables specified in the snapshot itself. Finally, GHC itself ships with a number of libraries and executables, which forms the global database. To get a quick idea of this, we can look at the output of the stack exec -- ghc-pkg list command in our helloworld project:
/home/michael/.stack/programs/x86_64-linux/ghc-7.10.2/lib/ghc-7.10.2/package.conf.d
Cabal-1.22.4.0
array-0.5.1.0
base-4.8.1.0
bin-package-db-0.0.0.0
binary-0.7.5.0
bytestring-0.10.6.0
containers-0.5.6.2
deepseq-1.4.1.1
directory-1.2.2.0
filepath-1.4.0.0
ghc-7.10.2
ghc-prim-0.4.0.0
haskeline-0.7.2.1
hoopl-3.10.0.2
hpc-0.6.0.2
integer-gmp-1.0.0.0
pretty-1.1.2.0
process-1.2.3.0
rts-1.0
template-haskell-2.10.0.0
terminfo-0.4.0.1
time-1.5.0.1
transformers-0.4.2.0
unix-2.7.1.0
xhtml-3000.2.1
/home/michael/.stack/snapshots/x86_64-linux/nightly-2015-08-26/7.10.2/pkgdb
stm-2.4.4
/home/michael/helloworld/.stack-work/install/x86_64-linux/nightly-2015-08-26/7.10.2/pkgdb
acme-missiles-0.3
helloworld-0.1.0.0
I did the same experiment on windows, but the results are different:
Create a new project by stack new helloworld
Edit helloworld/src/Lib.hs as following
module Lib
( someFunc
) where
import Acme.Missiles
someFunc :: IO ()
someFunc = launchMissiles
Edit helloworld/package.yaml as following
dependencies:
- base >= 4.7 && < 5
- text
- filepath
- containers
- acme-missiles
Since acme-missiles be not in LTS, so I add a extra-deps: in helloworld/stack.yaml
extra-deps:
- acme-missiles-0.3 # not in the LTS
stack build and success, log as following
E:\work-category-theory\helloworld>stack build
Stack has not been tested with GHC versions above 8.6, and using 8.8.3, this may fail
Stack has not been tested with Cabal versions above 2.4, but version 3.0.1.0 was found, this may fail
acme-missiles> configure
acme-missiles> Configuring acme-missiles-0.3...
acme-missiles> build
acme-missiles> Preprocessing library for acme-missiles-0.3..
acme-missiles> Building library for acme-missiles-0.3..
acme-missiles> [1 of 2] Compiling Acme.Missiles
acme-missiles> [2 of 2] Compiling Acme.Missiles.STM
acme-missiles> copy/register
acme-missiles> Installing library in C:\sr\snapshots\c1955c78\lib\x86_64-windows-ghc-8.8.3\acme-missiles-0.3-5Q3zlWTjrQa
Fyz88eRyQT2
acme-missiles> Registering library for acme-missiles-0.3..
Building all executables for `helloworld' once. After a successful build of all of them, only specified executables will
be rebuilt.
helloworld > configure (lib + exe)
Configuring helloworld-0.1.0.0...
helloworld > build (lib + exe)
Preprocessing library for helloworld-0.1.0.0..
Building library for helloworld-0.1.0.0..
[1 of 2] Compiling Lib
[2 of 2] Compiling Paths_helloworld
Preprocessing executable 'helloworld-exe' for helloworld-0.1.0.0..
Building executable 'helloworld-exe' for helloworld-0.1.0.0..
[1 of 2] Compiling Main
[2 of 2] Compiling Paths_helloworld
Linking .stack-work\dist\29cc6475\build\helloworld-exe\helloworld-exe.exe ...
helloworld > copy/register
Installing library in E:\work-category-theory\helloworld\.stack-work\install\5056a8ea\lib\x86_64-windows-ghc-8.8.3\hello
world-0.1.0.0-BBUUJBmDe2RHSTnItHQtB0
Installing executable helloworld-exe in E:\work-category-theory\helloworld\.stack-work\install\5056a8ea\bin
Registering library for helloworld-0.1.0.0..
Completed 2 action(s).
Now call stack exec -- ghc-pkg list
E:\work-category-theory\helloworld>stack exec -- ghc-pkg list
Stack has not been tested with GHC versions above 8.6, and using 8.8.3, this may fail
Stack has not been tested with Cabal versions above 2.4, but version 3.0.1.0 was found, this may fail
C:\Users\Chansey\AppData\Local\Programs\stack\x86_64-windows\ghc-8.8.3\lib\package.conf.d
Cabal-3.0.1.0
Win32-2.6.1.0
array-0.5.4.0
base-4.13.0.0
binary-0.8.7.0
bytestring-0.10.10.0
containers-0.6.2.1
deepseq-1.4.4.0
directory-1.3.6.0
filepath-1.4.2.1
(ghc-8.8.3)
ghc-boot-8.8.3
ghc-boot-th-8.8.3
ghc-compact-0.1.0.0
ghc-heap-8.8.3
ghc-prim-0.5.3
ghci-8.8.3
haskeline-0.7.5.0
hpc-0.6.0.3
integer-gmp-1.0.2.0
libiserv-8.8.3
mtl-2.2.2
parsec-3.1.14.0
pretty-1.1.3.6
process-1.6.8.0
rts-1.0
stm-2.5.0.0
template-haskell-2.15.0.0
text-1.2.4.0
time-1.9.3
transformers-0.5.6.2
xhtml-3000.2.2.1
C:\sr\snapshots\c1955c78\pkgdb
acme-missiles-0.3
E:\work-category-theory\helloworld\.stack-work\install\5056a8ea\pkgdb
helloworld-0.1.0.0
You can see that my outputs are different from the document.
The question is:
Why acme-missiles-0.3 is in C:/sr/snapshots/ rather than /helloworld/.stack-work? (Note that, in windows, C:/sr/ be equivalent to ~/.stack)
Also, in the FAQ of the document from https://docs.haskellstack.org/en/stable/faq/, it mentioned that
Where is stack installed and will it interfere with ghc (etc) I already have installed?
Stack itself is installed in normal system locations based on the mechanism you used (see the Install and upgrade page). Stack installs the Stackage libraries in ~/.stack and any project libraries or extra dependencies in a .stack-work directory within each project's directory. None of this should affect any existing Haskell tools at all.
acme-missiles-0.3 is extra dependencies, why in my experiment, it is in ~/.stack rather than .stack-work directory within project's directory?
Thanks.