git tag

git tag -a annotation -m "some message"

The latter has its own annotator person and date and it can include a messge provided by the -m flag. 

$ mkdir experiment
$ cd experiment/
$ git init .
Initialized empty Git repository in /home/gabor/experiment/.git/


$ touch README
$ git add .
$ git commit -m "add readme"
[master (root-commit) ab44956] add readme
 1 file changed, 0 insertions(+), 0 deletions(-)
 create mode 100644 README


$ echo "Hello World" > README
$ git add .
$ git commit -m "add hw"
[master 1f619d4] add hw
 1 file changed, 1 insertion(+)


$ git tag simple
$ git tag -a annotated -m message


$ git show HEAD
commit 1f619d4acb900ddfa1d69bbc7d0d0a59b3a184ee
Author: Gabor Szabo <gabor@twiggle.com>
Date:   Tue Apr 30 14:04:12 2019 +0300

    add hw

diff --git a/README b/README
index e69de29..557db03 100644
--- a/README
+++ b/README
@@ -0,0 +1 @@
+Hello World


$ git show simple
commit 1f619d4acb900ddfa1d69bbc7d0d0a59b3a184ee
Author: Gabor Szabo <gabor@twiggle.com>
Date:   Tue Apr 30 14:04:12 2019 +0300

    add hw

diff --git a/README b/README
index e69de29..557db03 100644
--- a/README
+++ b/README
@@ -0,0 +1 @@
+Hello World


$ git show annotated
tag annotated
Tagger: Gabor Szabo <gabor@twiggle.com>
Date:   Tue Apr 30 14:04:28 2019 +0300

message

commit 1f619d4acb900ddfa1d69bbc7d0d0a59b3a184ee
Author: Gabor Szabo <gabor@twiggle.com>
Date:   Tue Apr 30 14:04:12 2019 +0300

    add hw

diff --git a/README b/README
index e69de29..557db03 100644
--- a/README
+++ b/README
@@ -0,0 +1 @@
+Hello World