WIP: Migrate Wiki content over to src/docs

docs/git_tips.md

+When UsingGit, there are a few tips that are particularly useful when working on the Chromium codebase, especially due to its size.
+
+See also GitCookbook.
+
+Remember the basic git convention:
+> `git` _`COMMAND`_ `[`_`FLAGS`_`]` `[`_`ARGUMENTS`_`]`
+Various git commands have underlying executable with a hyphenated name, such as `git-grep`, but these can also be called via the `git` wrapper script as `git grep` (and `man` should work either way too).
+
+## Git references
+
+The following resources can provide background on how Git works:
+
+  * [Git-SVN Crash Course](http://git-scm.com/course/svn.html) -- this crash course is useful for Subversion users switching to Git.
+  * [Think Like (a) Git](http://think-like-a-git.net/) -- does a great job of explaining the main purpose of Git's operations.
+  * [Git User's Manual](http://schacon.github.com/git/user-manual.html) -- a great resource to learn more about how to use Git properly.
+  * [A Visual Git Reference](http://marklodato.github.com/visual-git-guide/index-en.html) -- a resource that explains various Git operations for visual reasons.
+  * [Git Cheat Sheet](http://cheat.errtheblog.com/s/git) -- now that you understand Git, here's a cheat sheet to quickly remind you of all the commands you need.
+
+## Committing changes
+For a simple workflow (always commit all changed files, don't keep local revisions), the following script handles check; you may wish to call it `gci` (git commit) or similar.
+
+Amending a single revision is generally easier for various reasons, notably for rebasing and for checking that CLs have been committed. However, if you don't use local revisions (a local branch with multiple revisions), you should make sure to upload revisions periodically to code review if you ever need to go to an old version of a CL.
+```
+#!/bin/bash
+# Commit all, amending if not initial commit.
+if git status | grep -q "# Your branch is ahead of 'master' by 1 commit."
+then
+  git commit --all --amend
+else
+  git commit --all  # initial, not amendment
+fi
+```
+
+## Listing and changing branches
+```
+git branch  # list branches
+git checkout -  # change to last branch
+```
+To quickly list the 5 most recent branches, add the following to `.gitconfig` in the `[alias]` section:
+```
+last5 = "!git for-each-ref --sort=committerdate refs/heads/ --format='%(committerdate:short) %(refname:short)' | tail -5 | cut -c 12-"
+```
+
+A nicely color-coded list, sorted in descending order by date, can be made by the following bash function:
+```
+git-list-branches-by-date() {
+  local current_branch=$(git rev-parse --symbolic-full-name --abbrev-ref HEAD)
+  local normal_text=$(echo -ne '\E[0m')
+  local yellow_text=$(echo -ne '\E[0;33m')
+  local yellow_bg=$(echo -ne '\E[7;33m')
+  git for-each-ref --sort=-committerdate \
+      --format=$'  %(refname:short)  \t%(committerdate:short)\t%(authorname)\t%(objectname:short)' refs/heads \
+      | column -t -s $'\t' -n \
+      | sed -E "s:^  (${current_branch}) :* ${yellow_bg}\1${normal_text} :" \
+      | sed -E "s:^  ([^ ]+):  ${yellow_text}\1${normal_text}:"
+}
+```
+
+## Searching
+Use `git-grep` instead of `grep` and `git-ls-files` instead of `find`, as these search only files in the index or _tracked_ files in the work tree, rather than all files in the work tree.
+
+Note that `git-ls-files` is rather simpler than `find`, so you'll often need to use `xargs` instead of `-exec` if you want to process matching files.
+
+## Global changes
+To make global changes across the source tree, it's often easiest to use `sed` with `git-ls-files`, using `-i` for in-place changing (this is generally safe, as we don't use symlinks much, but there are few places that do). Remember that you don't need to use `xargs`, since sed can take multiple input files. E.g., to strip trailing whitespace from C++ and header files:
+```
+ sed -i -E 's/\s+$//' $(git ls-files '*.cpp' '*.h')
+```
+
+You may also find `git-grep` useful for limiting the scope of your changes, using `-l` for listing files.
+```
+ sed -i -E '...' $(git grep -lw Foo '*.cpp' '*.h')
+```
+
+Remember that you can restrict sed actions to matching (or non-matching) lines. For example, to skip lines with a line comment, use the following:
+```
+  '\,//, ! s/foo/bar/g'
+```
+## Diffs
+```
+ git diff --shortstat
+```
+Displays summary statistics, such as:
+```
+ 2104 files changed, 9309 insertions(+), 9309 deletions(-)
+```