Veja o que você configurou em core.pager. Você provavelmente definiu como less sem o sinalizador -X definido. Ter esse conjunto de bandeiras impedirá que less apague a tela ao sair.
Se for esse o caso, acesse ~/.gitconfig e edite pager na seção [core] . Eu tenho o meu definido como -FRSX .
$ git config --get core.pager
less -FRSX
E, para sua conveniência, isso é da página less man descrevendo o significado de cada um desses sinalizadores:
-F or --quit-if-one-screen
Causes less to automatically exit if the entire file can be displayed on the first screen.
-R or --RAW-CONTROL-CHARS
Like -r, but only ANSI "color" escape sequences are output in "raw" form. Unlike -r, the screen appearance is maintained correctly in most cases. ANSI "color" escape sequences are sequences of the form:
ESC [ ... m
where the "..." is zero or more color specification characters For the purpose of keeping track of screen appearance, ANSI color escape sequences are assumed to not move the cursor. You can make less think that characters other than "m" can end ANSI
color escape sequences by setting the environment variable LESSANSIENDCHARS to the list of characters which can end a color escape sequence. And you can make less think that characters other than the standard ones may appear between the ESC and the m
by setting the environment variable LESSANSIMIDCHARS to the list of characters which can appear.
-S or --chop-long-lines
Causes lines longer than the screen width to be chopped (truncated) rather than wrapped. That is, the portion of a long line that does not fit in the screen width is not shown. The default is to wrap long lines; that is, display the remainder on the
next line.
-X or --no-init
Disables sending the termcap initialization and deinitialization strings to the terminal. This is sometimes desirable if the deinitialization string does something unnecessary, like clearing the screen.