How does git quickly merge all remote branches into a local test branch?

for example:

a,b,c 3
mytestmytest

current implementation: now I am merging other branches one by one through git merge XXX , but it doesn"t feel efficient. Do you want to know who has some better operations?

Git
Mar.04,2021
MySQL Query : SELECT * FROM `codeshelper`.`v9_news` WHERE status=99 AND catid='6' ORDER BY rand() LIMIT 5
MySQL Error : Disk full (/tmp/#sql-temptable-64f5-1e46dd6-44bec.MAI); waiting for someone to free some space... (errno: 28 "No space left on device")
MySQL Errno : 1021
Message : Disk full (/tmp/#sql-temptable-64f5-1e46dd6-44bec.MAI); waiting for someone to free some space... (errno: 28 "No space left on device")
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