I added a file to the index with:
git add somefile.txt
I then got the SHA1 for this file with:
git hash-object somefile.txt
I now have a SHA1 and I would like to retrieve the filename of the object in the index using the SHA1.
git show 5a5bf28dcd7944991944cc5076c7525439830122
This command returns the file contents but not the name of the file.
How do I get the full filename and path back from the SHA1?
There's no such direct mapping in git as the name of the file is part of the tree object that contains the file, not of the blob object that is the file's contents.
It's not a usual operation to want to retrieve a file name from a SHA1 hash so perhaps you could expand on a real world use case for it?
If you're looking at current files (i.e. the HEAD commit) you can try the following.
git ls-tree -r HEAD | grep <SHA1>
If you want to find the contents in previous commits you'll need to do something more like this.
git rev-list <commit-list> | \
xargs -n1 -iX sh -c "git ls-tree -r X | grep <SHA1> && echo X"