Merge branch 'sheets' of https://github.com/dufferzafar/chris-cheat into dufferzafar-sheets

* 'sheets' of https://github.com/dufferzafar/chris-cheat:
  New Sheet: ffmpeg - fast audio video encoder
  Git cheats: Shallow clones & Submodule update
  Git cheats: Change date of existing commit

cheat/cheatsheets/ffmpeg

@@ -0,0 +1,12 @@
+# Print file metadata etc.
+ffmpeg -i path/to/file.ext
+
+# Convert all m4a files to mp3
+for f in *.m4a; do ffmpeg -i "$f" -acodec libmp3lame -ab 320k "${f%.m4a}.mp3"; done
+
+# Listen to 10 seconds of audio from a video file
+#
+# -ss : start time
+# -t  : seconds to cut
+# -autoexit : closes ffplay as soon as the audio finishes
+ffmpeg -ss 00:34:24.85 -t 10 -i path/to/file.mp4 -f mp3 pipe:play | ffplay -i pipe:play -autoexit

cheat/cheatsheets/git

@@ -22,6 +22,14 @@ git commit --date="`date --date='2 day ago'`"
 git commit --date="Jun 13 18:30:25 IST 2015"
 # more recent versions of Git also support --date="2 days ago" directly
 
+# To change the date of an existing commit
+git filter-branch --env-filter \
+    'if [ $GIT_COMMIT = 119f9ecf58069b265ab22f1f97d2b648faf932e0 ]
+     then
+         export GIT_AUTHOR_DATE="Fri Jan 2 21:38:53 2009 -0800"
+         export GIT_COMMITTER_DATE="Sat May 19 01:01:01 2007 -0700"
+     fi'
+
 # To removed staged and working directory changes
 git reset --hard
 
@@ -86,3 +94,13 @@ git diff --no-index path/to/file/A path/to/file/B
 # To pull changes while overwriting any local commits
 git fetch --all
 git reset --hard origin/master
+
+# Update all your submodules
+git submodule update --init --recursive
+
+# Perform a shallow clone to only get latest commits
+# (helps save data when cloning large repos)
+git clone --depth 1 <remote-url>
+
+# To unshallow a clone
+git pull --unshallow