Doc: explain invocation of delta by git

1 files changed, 8 insertions, 2 deletions

diff --git a/README.md b/README.md
index 6198cd9f..86cb7700 100644
--- a/README.md
+++ b/README.md
@@ -323,9 +323,15 @@ Delta also handles unified diff format, e.g. `diff -u a.txt b.txt | delta`.
 
 For Mercurial, you can add delta, with its command line options, to the `[pager]` section of `.hgrc`.
 
-#### Environment
+#### How delta works
+
+If you configure delta in gitconfig as above, then git will automatically send its output to delta.
+Delta in turn passes its own output on to a "real" pager.
+Note that git will only send its output to delta if git believes that its output is going to a terminal (a "tty") for a human to read.
+In other words, if you do something like `git diff | grep ...` then you don't have to worry about delta changing the output from git, because delta will never be invoked at all.
+If you need to force delta to be invoked when git itself would not invoke it, then you can always pipe to delta explicitly.
+For example, `git diff | delta | something-that-expects-delta-output-with-colors` (in this example, git's output is being sent to a pipe, so git itself will not invoke delta).
 
-Delta acts as a pager for git's output, and delta in turn passes its own output on to a "real" pager.
 The pager that delta uses is determined by consulting the following environment variables (in this order):
 
 - `DELTA_PAGER`