How to monitor `git diff` progress?

```
debian@ovh-r3-256-debian-13:~/upstream/firefox/dom/base$ git diff --stat Navigator.cpp
perl: warning: Setting locale failed.
perl: warning: Please check that your locale settings:
LANGUAGE = (unset),
LC_ALL = (unset),
LC_CTYPE = (unset),
LC_NUMERIC = "fr_FR.UTF-8",
LC_COLLATE = (unset),
LC_TIME = "en_GB.UTF-8",
LC_MESSAGES = (unset),
LC_MONETARY = "fr_FR.UTF-8",
LC_ADDRESS = "fr_FR.UTF-8",
LC_IDENTIFICATION = "fr_FR.UTF-8",
LC_MEASUREMENT = "fr_FR.UTF-8",
LC_PAPER = "fr_FR.UTF-8",
LC_TELEPHONE = "fr_FR.UTF-8",
LC_NAME = "fr_FR.UTF-8",
LANG = "C.UTF-8"
are supported and installed on your system.
perl: warning: Falling back to a fallback locale ("C.UTF-8").
Waiting for data... (^X or interrupt to abort)
```
May 25, 5:00pm

The "Waiting for data..." message comes from your pager (usually less), not git diff itself. git diff computes the entire diff in memory before displaying it, so no progress is shown by default.

🔧 Quick Fixes

1️⃣ Disable the pager (show output immediately)

bash
git --no-pager diff --stat Navigator.cpp

or set it permanently:

bash
git config --global core.pager cat

2️⃣ Fix locale warnings (optional, but cleans up noise)

bash
export LC_ALL=C.UTF-8
export LANG=C.UTF-8

Add these to your ~/.bashrc or ~/.zshrc to persist.

📊 Monitoring Progress for Large Diffs

Show file list first
git diff --name-only
Fast, lists changed files only
Faster stat summary
git diff --stat --numstat
Avoids full diff computation
Limit to 1 file
git diff --stat Navigator.cpp
Already what you’re doing
Use pv (Pipe Viewer)
git diff Navigator.cpp | pv -s $(wc -c < Navigator.cpp) > /dev/null
Estimates progress (not precise)
Debug with strace
strace -f git diff --stat Navigator.cpp
Shows system calls (advanced)

⚡ Best Approach for Large Repos

  1. Check file size first:

    bash
    ls -lh Navigator.cpp

    If it’s >100MB, git diff may take a while.

  2. Compare in chunks:

    bash
    git diff --stat HEAD~1 -- Navigator.cpp  # Compare with last commit

  3. Use git difftool for interactive diffs (e.g., with vimdiff or meld).

🎯 Summary

  • Immediate fix: Use git --no-pager diff --stat Navigator.cpp
  • For large files: Break into smaller diffs or use --name-only first.
  • Locale warnings: Set LC_ALL=C.UTF-8 to suppress them.
May 25, 5:01pm

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