migrate: properly escape blob filenames

[pyckle]

Please consider this minor PR to fix the below bug. I added a unit test. I hope this is straightforward.

Describe the bug
When files have a combination of spaces and parentheses/dashes, git lfs migrate import produces invalid filenames in .gitattributes

To Reproduce
Steps to reproduce the behavior:

#!/bin/bash -ex
mkdir testrepo
cd testrepo
git init .
dd if=/dev/urandom of='./test - special.bin' bs=1M count=1
dd if=/dev/urandom of='./test (test2) special.bin' bs=1M count=1
dd if=/dev/urandom of='./test * ** special.bin' bs=1M count=1
git add .
git commit -am 'my first commit'
git lfs migrate import --everything --above 512KB
git add .gitattributes
cat .gitattributes

Expected behavior
.gitattributes should escape the filenames. Ideally they should be in double quotes (c-style escaping), but pattern escaping also should be OK.

System environment
Debian 10.10 and git lfs 3.0.1

Output of git lfs env
The output of running git lfs env as a code block.

$ git lfs env
git-lfs/3.0.1 (GitHub; linux amd64; go 1.17.1)
git version 2.33.0

LocalWorkingDir=/home/andrewp/testing/testrepo
LocalGitDir=/home/andrewp/testing/testrepo/.git
LocalGitStorageDir=/home/andrewp/testing/testrepo/.git
LocalMediaDir=/home/andrewp/testing/testrepo/.git/lfs/objects
LocalReferenceDirs=
TempDir=/home/andrewp/testing/testrepo/.git/lfs/tmp
ConcurrentTransfers=8
TusTransfers=false
BasicTransfersOnly=false
SkipDownloadErrors=false
FetchRecentAlways=false
FetchRecentRefsDays=7
FetchRecentCommitsDays=0
FetchRecentRefsIncludeRemotes=true
PruneOffsetDays=3
PruneVerifyRemoteAlways=false
PruneRemoteName=origin
LfsStorageDir=/home/andrewp/testing/testrepo/.git/lfs
AccessDownload=none
AccessUpload=none
DownloadTransfers=basic,lfs-standalone-file,ssh
UploadTransfers=basic,lfs-standalone-file,ssh
GIT_EXEC_PATH=/home/andrewp/local/libexec/git-core
git config filter.lfs.process = "git-lfs filter-process"
git config filter.lfs.smudge = "git-lfs smudge -- %f"
git config filter.lfs.clean = "git-lfs clean -- %f"

[pyckle]

Please rerun the MacOS build - I think it was a spurious failure related to #4674

[bk2204]

Hey,

Thanks for the patch, and welcome to Git LFS! This looks good, and once CI goes green here, I'll go ahead and merge it.

[pyckle]

Sounds good. Thanks @bk2204 👍