create tree without using staging area

Question

In the git internals chapter of git-scm book there is an example of how git tree can be created:

Git normally creates a tree by taking the state of your staging area or index and writing a series of tree objects from it. So, to create a tree object, you first have to set up an index by staging some files.

And then they list commands that I can use to create the tree. My question is whether I can create a tree without using index (staging area)? For example instead of doing this:

git update-index --add --cacheinfo 100644 83baae618... test.txt

Use something like this:

git create tree --add --cacheinfo 100644 83baae618... test.txt

Update based on Ismail Badawi's anser:

$ echo 'making tree' | git hash-object -w --stdin
07dae42a0730df1cd19b0ac693c6894a02ed6ad0

and then

$ echo -e '100644 blob 07dae42a0730df1cd19b0ac693c6894a02ed6ad0 \maketree.txt' | git mktree
fatal: input format error: 100644 blob 07dae42a0730df1cd19b0ac693c6894a02ed6ad0 \maketree.txt

Answer 1

You can use git mktree, like this:

echo -e "100644 blob 83baae618...\ttest.txt" | git mktree

(You need to write echo -e because of the literal tab. This is a shell thing, not a git thing).

Note this creates a tree that only points to 83baae618, so it's not exactly the same as your update-index invocation, which adds to the index (which typically already points to other things). You can pass multiple lines to git mktree, each line describing one blob or tree.