Fix webhook commits wrong hash on HEAD reset (#16283)

Use `..` instead of `...` with `rev-list`. In combination with #16282 the receiver can get the correct commit. The behaviour is now like Github.

fixes #11802

modules/git/tests/repos/repo4_commitsbetween/HEAD

@@ -0,0 +1 @@
+ref: refs/heads/main

modules/git/tests/repos/repo4_commitsbetween/config

@@ -0,0 +1,7 @@
+[core]
+	repositoryformatversion = 0
+	filemode = false
+	bare = false
+	logallrefupdates = true
+	symlinks = false
+	ignorecase = true

modules/git/tests/repos/repo4_commitsbetween/logs/HEAD

@@ -0,0 +1,4 @@
+0000000000000000000000000000000000000000 fdc1b615bdcff0f0658b216df0c9209e5ecb7c78 KN4CK3R <admin@oldschoolhack.me> 1624915979 +0200	commit (initial): com1
+fdc1b615bdcff0f0658b216df0c9209e5ecb7c78 78a445db1eac62fe15e624e1137965969addf344 KN4CK3R <admin@oldschoolhack.me> 1624915993 +0200	commit: com2
+78a445db1eac62fe15e624e1137965969addf344 fdc1b615bdcff0f0658b216df0c9209e5ecb7c78 KN4CK3R <admin@oldschoolhack.me> 1624916008 +0200	reset: moving to HEAD~1
+fdc1b615bdcff0f0658b216df0c9209e5ecb7c78 a78e5638b66ccfe7e1b4689d3d5684e42c97d7ca KN4CK3R <admin@oldschoolhack.me> 1624916029 +0200	commit: com2_new

modules/git/tests/repos/repo4_commitsbetween/logs/refs/heads/main

@@ -0,0 +1,4 @@
+0000000000000000000000000000000000000000 fdc1b615bdcff0f0658b216df0c9209e5ecb7c78 KN4CK3R <admin@oldschoolhack.me> 1624915979 +0200	commit (initial): com1
+fdc1b615bdcff0f0658b216df0c9209e5ecb7c78 78a445db1eac62fe15e624e1137965969addf344 KN4CK3R <admin@oldschoolhack.me> 1624915993 +0200	commit: com2
+78a445db1eac62fe15e624e1137965969addf344 fdc1b615bdcff0f0658b216df0c9209e5ecb7c78 KN4CK3R <admin@oldschoolhack.me> 1624916008 +0200	reset: moving to HEAD~1
+fdc1b615bdcff0f0658b216df0c9209e5ecb7c78 a78e5638b66ccfe7e1b4689d3d5684e42c97d7ca KN4CK3R <admin@oldschoolhack.me> 1624916029 +0200	commit: com2_new

modules/git/tests/repos/repo4_commitsbetween/objects/78/a445db1eac62fe15e624e1137965969addf344

@@ -0,0 +1,3 @@
+x
<01><>M
+<EFBFBD>0@a<>=E<><45>̤I<CCA4><49><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>$<24>Zl<1A><><EFBFBD><EFBFBD><1C>|<7C>G<EFBFBD><47><EFBFBD>)<29>îm̊uO<75>"<22><><EFBFBD><EFBFBD>&`<02><>8Gt<>I<>7<EFBFBD>#n<>6%<25>09<30>)<29>8<><38>F<EFBFBD>(hl<><6C>@<40><><EFBFBD><EFBFBD>MuS<75><53>\<5C><><EFBFBD><EFBFBD>1<EFBFBD>y=<3D>%?i<>u<EFBFBD>"<22><0F>O
+<EFBFBD><EFBFBD>Dm<08>ڃ<06><>w<EFBFBD><77><1F>ź{p<>C_

modules/git/tests/repos/repo4_commitsbetween/refs/heads/main

@@ -0,0 +1 @@
+a78e5638b66ccfe7e1b4689d3d5684e42c97d7ca