git-heads.md: new blog entry

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+title: 2016-03 blogs
+linktitle: 2016-03
+parent: 2016
+ctime: 2016-03-01
+mtime: 2000-03-01

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+title: git-heads
+linktitle: git-heads
+parent: 2016-03
+ctime: 2016-03-17
+mtime: 2016-03-17
+
+# Using git-heads for branch summaries
+
+When merging code in [Git](http://git-scm.com), I often want to see an overview
+of the branches in my local clone, and the branches on the origin (remote).
+Some of the questions that I ask:
+
+* Which local branches are out of date with their upstream branches?
+* What topic branches are available on the remote (candidates to merge)?
+* What is the oldest, or newest, topic branch in terms of most recent commit?
+
+I've been getting answers to these questions using `gitk`, `git log` and `git
+branch`.  But when I started wanting to see a list of branch heads ordered by
+last author date, the tools at my disposal weren't getting the job done.  `git
+branch -vv` is close, but it doesn't order the branches by date, and always
+links tracking branches to their upstream branches.
+
+Enter [git-heads](https://github.com/seschwar/git-heads.git).  This is a great
+little utility, essentially generating output like `git log` but filtering to
+show only branch head commits.
+
+## Default git-heads output
+
+Ran with no arguments, [git-heads](https://github.com/seschwar/git-heads.git)
+produces output like the following:
+
+![Default git-heads output](images/git-heads-dflt.png)
+
+Considering [git-heads](https://github.com/seschwar/git-heads.git) as a filter
+for `git log`, this output is perfectly reasonable.
+
+## Customized git-heads output
+
+For my use cases, I typically want a list of branch heads that is more terse,
+and ordered by author date.
+[git-heads](https://github.com/seschwar/git-heads.git) supports a flexible set
+of options, so my desired output format was easy to achieve:
+
+    git-heads -a --author-date-order --format='format:%C(auto)%ad %h%d'
+
+The above command generates output like the following.  Notice that the branch
+head commits are ordered newest first, by author date in this case.  I think of
+this format as a variant of `git branch -vv`.
+
+![Terse git-heads output](images/git-heads-terse.png)
+
+This output form makes easy work of my original questions.
+
+* Which local branches are out of date?  After `git fetch`, out of date branches
+  are shown by the local branch and the remote branch having different commits,
+  with the newer of the two showing above the other in the output.
+
+* Which topic branches are on the remote?  Just pipe the
+  [git-heads](https://github.com/seschwar/git-heads.git) output to `grep
+  origin/topic/`.  I usually pipe instead to `grep topic/` so local topic
+  branches are also shown.
+
+## Changing git-heads default output format
+
+My preferred output format from
+[git-heads](https://github.com/seschwar/git-heads.git) requires an inconvenient
+command line.  The simple solution is to place the command in a shell script.
+Instead, I chose to make a small change to
+[git-heads](https://github.com/seschwar/git-heads.git) so that if it were
+executed with no arguments, default arguments would be retrieved the git config
+property `heads.dfltargs`, if present.  This is this property in my
+`~/.gitconfig` file:
+
+    $ git config heads.dfltargs
+    -a --author-date-order "--format=format:%C(auto)%ad %h%d"
+
+The change to [git-heads](https://github.com/seschwar/git-heads.git) is small
+and self contained:
+
+    diff --git c/git-heads w/git-heads
+    index 5d8a78f..288895b 100755
+    --- c/git-heads
+    +++ w/git-heads
+    @@ -157,5 +157,15 @@ main() {
+     }
+     
+     
+    +if test "$#" -eq 0; then
+    +    # Set a nice default args in .gitconfig, like:
+    +    # [heads]
+    +    #     dfltargs = -a --author-date-order \"--format=format:%C(auto)%ad %h%d\"
+    +
+    +    dfltargs=$(git config heads.dfltargs)
+    +    if test -n "$dfltargs"; then
+    +        eval main $dfltargs
+    +        exit 0
+    +    fi
+    +fi
+     main "$@"
+    -
+

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