From 9de1c8c551089074507d09046335fdb4c2434033 Mon Sep 17 00:00:00 2001
From: Andre Merzky <andre@merzky.net>
Date: Fri, 1 Dec 2017 12:22:18 +0100
Subject: [PATCH 1/3] implement an opt-in pipignore mechanism

```
(ve)  thinkie  merzky  ~/projects/pip  [master *] $ rm -rf data/
(ve)  thinkie  merzky  ~/projects/pip  [master *] $ unset PIP_IGNORE
(ve)  thinkie  merzky  ~/projects/pip  [master *] $ rm -f .pipignore
(ve)  thinkie  merzky  ~/projects/pip  [master *] $ time pip install --no-deps --upgrade .
Looking in indexes: https://pypi.python.org/simple, https://packagecloud.io/github/git-lfs/pypi/simple
Processing /home/merzky/projects/pip
Installing collected packages: pip
  Found existing installation: pip 10.0.0.dev0
    Uninstalling pip-10.0.0.dev0:
      Successfully uninstalled pip-10.0.0.dev0
  Running setup.py install for pip ... done
Successfully installed pip-10.0.0.dev0
r:0m3.421s  u:0m2.828s  s:0m0.604s
(ve)  thinkie  merzky  ~/projects/pip  [master *] $ mkdir data
(ve)  thinkie  merzky  ~/projects/pip  [master *] $ dd if=/dev/urandom of=data/test.dat count=$((2048*1024))
2097152+0 records in
2097152+0 records out
1073741824 bytes (1.1 GB, 1.0 GiB) copied, 15.17 s, 70.8 MB/s
(ve)  thinkie  merzky  ~/projects/pip  [master *] $ time pip install --no-deps --upgrade .
Looking in indexes: https://pypi.python.org/simple, https://packagecloud.io/github/git-lfs/pypi/simple
Processing /home/merzky/projects/pip
Installing collected packages: pip
  Found existing installation: pip 10.0.0.dev0
    Uninstalling pip-10.0.0.dev0:
      Successfully uninstalled pip-10.0.0.dev0
  Running setup.py install for pip ... done
Successfully installed pip-10.0.0.dev0
r:0m41.687s  u:0m3.420s  s:0m3.320s
(ve)  thinkie  merzky  ~/projects/pip  [master *] $ export PIP_IGNORE=.pipignore
(ve)  thinkie  merzky  ~/projects/pip  [master *] $ cat > .pipignore
  # and this

data

.pipignore # because, why not

(ve)  thinkie  merzky  ~/projects/pip  [master *] $ time pip install --no-deps --upgrade .
Looking in indexes: https://pypi.python.org/simple, https://packagecloud.io/github/git-lfs/pypi/simple
Processing /home/merzky/projects/pip
Installing collected packages: pip
  Found existing installation: pip 10.0.0.dev0
    Uninstalling pip-10.0.0.dev0:
      Successfully uninstalled pip-10.0.0.dev0
  Running setup.py install for pip ... done
Successfully installed pip-10.0.0.dev0
r:0m3.495s  u:0m2.780s  s:0m0.664s

```
---
 src/pip/_internal/download.py | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/src/pip/_internal/download.py b/src/pip/_internal/download.py
index d56a1bb3bb2..64b8b3f288b 100644
--- a/src/pip/_internal/download.py
+++ b/src/pip/_internal/download.py
@@ -690,11 +690,20 @@ def unpack_file_url(link, location, download_dir=None, hashes=None):
     """
     link_path = url_to_path(link.url_without_fragment)
 
+    # if a .pipignore' file location is set and exists, '#' style comments are stripped
+    ignored = list()
+    pipignore = os.environ.get('PIP_IGNORE')
+    if pipignore and os.path.isfile(pipignore):
+        with open(pipignore, 'r') as fin:
+            for line in fin.readlines():
+                ignored.extend(line.split('#')[0].strip().split())
+
     # If it's a url to a local directory
     if is_dir_url(link):
         if os.path.isdir(location):
             rmtree(location)
-        shutil.copytree(link_path, location, symlinks=True)
+        shutil.copytree(link_path, location, symlinks=True,
+                        ignore=shutil.ignore_patterns(*ignored))
         if download_dir:
             logger.info('Link is a directory, ignoring download_dir')
         return

From 33e4d977fcdd4d0fc6c4885232a75dd234a2d8a0 Mon Sep 17 00:00:00 2001
From: Andre Merzky <andre@merzky.net>
Date: Fri, 1 Dec 2017 12:24:27 +0100
Subject: [PATCH 2/3] expand documentation

---
 src/pip/_internal/download.py | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/src/pip/_internal/download.py b/src/pip/_internal/download.py
index 64b8b3f288b..4671857135b 100644
--- a/src/pip/_internal/download.py
+++ b/src/pip/_internal/download.py
@@ -690,7 +690,10 @@ def unpack_file_url(link, location, download_dir=None, hashes=None):
     """
     link_path = url_to_path(link.url_without_fragment)
 
-    # if a .pipignore' file location is set and exists, '#' style comments are stripped
+    # if a .pipignore' file location is set and exists, '#' style
+    # comments are stripped.  All other strings (space limited) are interpreted
+    # as glob-style pattersn to be passed to `shutil.copytree`, and are thus
+    # excluded from the file cloning operation.
     ignored = list()
     pipignore = os.environ.get('PIP_IGNORE')
     if pipignore and os.path.isfile(pipignore):

From 15980b37079313e721a9bb9f170b5a40e9ab6981 Mon Sep 17 00:00:00 2001
From: Andre Merzky <andre@merzky.net>
Date: Fri, 1 Dec 2017 12:30:28 +0100
Subject: [PATCH 3/3] add news fragment

---
 news/2195.feature | 1 +
 1 file changed, 1 insertion(+)
 create mode 100644 news/2195.feature

diff --git a/news/2195.feature b/news/2195.feature
new file mode 100644
index 00000000000..947d6cd2f36
--- /dev/null
+++ b/news/2195.feature
@@ -0,0 +1 @@
+Add supporte for a `PIP_IGNORE` environment setting, which, when pointing to a valid file, causes `pip install` to ignore all file patterns listed in there.  This can speed up installations from large source trees.