Here is a quick solution for git-bash tree command error, with alternate and inbuilt features of gitbash.
Code:
admin@devopsrun MINGW64 ~
$ tree
bash: tree: command not found

Solution #1. Using find command


The command find is available inbuilt with git bash(like all portable bash such as cygwin). You may use the command find from the directory where you want to list files in the current and subdirectories, as shown below. 
Example:
Code:
admin@devopsrun MINGW64 ~/project
$ find
.
./config
./config/cfg1.properties
./config/cfg2.properties
./config/cfg3.properties
./config/cfg4.properties
./config/cfg5.properties
./file1.txt
./file2.txt

Solution #2. Using the ls command


The ls command with options l and R can list all files and folders in the current and sub directories.
l - is for long listing
R - recursive listing
Example:
Code:
$ ls -lR
.:
total 0
drwxr-xr-x 1 admin 197121 0 Feb 10 09:46 config/
-rw-r--r-- 1 admin 197121 0 Feb 10 09:45 file1.txt
-rw-r--r-- 1 admin 197121 0 Feb 10 09:45 file2.txt

./config:
total 0
-rw-r--r-- 1 admin 197121 0 Feb 10 09:46 cfg1.properties
-rw-r--r-- 1 admin 197121 0 Feb 10 09:46 cfg2.properties
-rw-r--r-- 1 admin 197121 0 Feb 10 09:46 cfg3.properties
-rw-r--r-- 1 admin 197121 0 Feb 10 09:46 cfg4.properties
-rw-r--r-- 1 admin 197121 0 Feb 10 09:46 cfg5.properties

Note, these options will work in any flavours of Linux distributions, where you have a bash shell, such as in docker containers