Merge pull request #248 from fsprojects/useful-git-script

Useful script to backdate git tags

backdate-tags.cmd

@@ -0,0 +1,60 @@
+@echo off
+
+REM Batch file to override the date and/or message of existing tag, or create a new
+REM tag that takes the same date/time of an existing commit.
+REM 
+REM Usage:
+REM  > backdate-tags.cmd v0.1.1 "New message"
+REM
+REM How it works:
+REM  * checkout the commit at the moment of the tag
+REM  * get the date/time of that commit and store in GIT_COMMITER_DATE env var
+REM  * recreate the tag (it will now take the date of its commit)
+REM  * push tags changes to remove (with --force)
+REM  * return to HEAD
+REM
+REM PS: 
+REM  * these escape codes are for underlining the headers so they stand out between all GIT's output garbage
+REM  * the back-dating trick is taken from here: https://stackoverflow.com/questions/21738647/change-date-of-git-tag-or-github-release-based-on-it
+
+ECHO.
+ECHO List existing tags:
+git tag -n
+
+ECHO.
+ECHO Checkout to tag:
+git checkout tags/%1
+
+REM Output the first string, containing the date of commit, and put it in a file
+REM then set the contents of that file to env var GIT_COMMITTER_DATE (which in turn is needed to enable back-dating)
+REM then delete the temp file
+ECHO.
+ECHO Retrieve original commit date
+
+git show --format=%%aD | findstr "^[MTWFS][a-z][a-z],.*" > _date.tmp
+< _date.tmp (set /p GIT_COMMITTER_DATE=)
+del _date.tmp
+
+ECHO Committer date for tag: %GIT_COMMITTER_DATE%
+ECHO Overriding tag '%1' with text: %2
+ECHO.
+REM Override (with -af) the tag, if it exists (no quotes around %2)
+git tag -af %1 -m %2
+
+ECHO.
+ECHO Updated tag:
+git tag --points-at HEAD -n
+ECHO.
+
+REM Push to remove and override (with --force)
+ECHO Push changes to remote
+git push --tags --force
+
+REM Go back to original HEAD
+ECHO.
+ECHO Back to original HEAD
+git checkout -
+
+ECHO.
+ECHO List of all tags
+git tag -n