shows the difference between the working directory and index

git difftool HEAD

Shows the difference between the commits in some of the difftool apps (that is previously configured)

git difftool a8098222d481b2c4249e09cdf639427b237a1d8f 17d3352bd6486e4c34bbfc51053c7b86911458da

Shows the difference between

login.frm

files from different commits in default diff.tool

git difftool a8098222d481b2c4249e09cdf639427b237a1d8f 17d3352bd6486e4c34bbfc51053c7b86911458da login.frm

If the diff.tool is not configured, the default console diff tool

vimdiff

will be used instead. ... Shows what default diff.tool is

git config --global merge.tool

Shows what meld.path is

git config --global mergetool.meld.path

Configure merge tool and set

meld

as default

git config --global merge.tool "meld"
git config --global mergetool.meld.path "C:\Program Files (x86)\Meld\Meld.exe"

Configure difftool prompt to false

git config --global difftool.prompt false